t/CSB   LIBRARY 


NOTES 


CHEMICAL  LECTURES 


SECOND-YEAR  STUDENTS 


MEDICAL  DEPARTMENT  OF  THE  UNIVERSITY 
OF  PENNSYLVANIA. 


PUBLISHED  BY  AUTHORITY  OF  PROF.  THEO.  G.  WORMLEY. 

BY 

JOHN  MARSHALL. 


PHILADELPHIA: 

AVIL  PRINTING  COMPANY. 

1894. 


Copyright,  1894,  by  JOHN  MARSHALL. 


THE  following  notes,  by  Dr.  Marshall,  of  my  Lectures  on 
Chemistry,  for  students,  have  been  published  with  my  consent  and 
authority. 

THEODORE  G.  WORMLEY. 


NOTES 


ON 


CHEMICAL  LECTURES. 


ORGANIC   CHEMISTRY. 

THE  production  of  organic  compounds  was  supposed  to  be 
due  to  the  influence  of  a  so-called  vital  force.  This  supposi- 
tion was  shown  to  be  fallacious  when  organic  compounds  were 
produced  artificially  (by  synthesis). 

Liebig  defined  organic  chemistry  as  the  chemistry  of  the 
compound  radicals.  This  definition  is  faulty  because  there 
are  radicals,  as  NHt,  SO3,  etc.,  in  the  domain  of  inorganic 
chemistry. 

The  names  compound  radical  and  radical  are  synonymous. 

A  radical  is  a  chemical  combination  of  two  or  more  ele- 
ments capable  of  playing  the  part  of  an  elementary  form  of 
matter. 

Organic  chemistry  has  been  defined  as  the  chemistry  of 
the  compounds  of  carbon.  It  must  be  remembered  that  there 
are  two  compounds  containing  carbon  in  the  domain  of 
inorganic  chemistry,  CO  and  CO2. 

The  latest  definition  of  organic  chemistry  is, — the  chem- 
istry of  the  hydrocarbon  compounds  and  their  derivatives. 
This  definition  applies  to  all  carbon  compounds  except  HCN 
(hydrocyanic  acid)  and  CN  (cyanogen). 

The  number  of  elements  entering  into  the  composition  of 
organic  compounds  is  comparatively  small,  but  the  number  of 
atoms  in  a  molecule  of  a  compound  may  be  very  large. 

Organic  compounds  may  be  composed  of  simply  carbon 
and  hydrogen.  Such  compounds  are  termed  hydrocarbons, 
as  Ci0H1G,  oil  of  turpentine,  CH4,  methane. 

(5) 


6  NOTES  ON  CHEMICAL  LECTURES. 

CN,  cyanogen  is  an  organic  compound  composed  of  two 
elements. 

Other  organic  compounds  may  be  composed  of  three  ele- 
ments,— namely,  carbon,  hydrogen,  and  oxygen.  Compounds 
of  these  three  elements  containing  the  hydrogen  and  oxygen 
atoms  in  the  proportion  to  form  water  are  called  carbohy- 
drates, as  C6H10O5,  starch,  C6H12O6,  glucose,  in  the  latter  there 
are  H12O6  =  6H2O. 

There  are  three  principal  groups  of  carbohydrates : 
The 

Glucose  group. 

Saccharose  group. 

Amylose  group. 

Organic  compounds  may  be  composed  of  four  elements, 
carbon,  hydrogen,  oxygen,  and  nitrogen.  Compounds 
containing  nitrogen  are  termed  nitrogenous  or  azotized,  as 
CO(NH2)2,  urea,  C5H4N4O3,  uric  acid. 

Some  compounds  are  composed  of  only  carbon  and  nitro- 
gen, as  CN,  cyanogen,  and  others  of  carbon,  nitrogen,  and 
hydrogen,  as  HCN,  hydrocyanic  acid. 

HCN,  hydrocyanic  acid,  may  be  looked  upon  as  CH4,  me- 
thane, in  which  three  atoms  of  H  have  been  replaced  by  an 

atom  of  triad  nitrogen,  as  C  ^TT 

A  few  organic  compounds  contain  carbon,  hydrogen,  oxy- 
gen, nitrogen,  and  sulphur,  as  CgoiHg^N^O^Sa,  egg-albumen. 
Some  few  contain  phosphorus,  as  C^H^NPOg,  lecithin. 

A  very  few  organic  compounds  contain,  in  addition  to 
carbon,  hydrogen,  oxygen,  nitrogen,  and  sulphur,  a  metal, — as 
iron  in  C636H1025N164O189FeS3O2,  oxyhaemoglobin,  the  molecular 
weight  of  which  is  14161. 

All  organic  compounds  occurring  in  nature  may  be  con- 
sidered as  falling  under  the  above  classification.  By  chemical 
means  nearly  all  of  the  elements  may  be  introduced  into 
organic  chemical  compounds. 

The  number  of  possible  combinations  of  these  elements  to 
produce  new  organic  compounds  is  almost  infinite.  Ordinarily, 
however,  only  fourteen  or  fifteen  elements  are  concerned  in 
chemical  combinations  in  organic  chemistry. 


•"°  -»w. 


NOTES  ON  CHEMICAL  LETCURES.  7 

Organic  compounds  containing  mercury,  copper,  gold,  etc., 
and  iodine,  bromine,  chlorine,  etc.,  may  be  produced  artificially 
by  chemical  means.  These  compounds  do  not  occur  already 
formed  in  nature. 

An  organic  body  is  an  aggregation  of  distinct  organic 
compounds  called  proximate  constituents.  An  organic  body 
may  also  contain  inorganic  compounds.  Examples,  conium 
maculatum,  opium,  etc.  The  percentage  proportion  of  the 
proximate  constituents  contained  in  an  organic  body  is  not 
definite, — i.  e.,  two  or  three  samples  of  opium  selected  at 
random  will  not  contain,  except  by  chance,  the  same  percent- 
age of  morphine. 

A  proximate  principle  is  an  organic  compound  which  is 
contained  in  an  organic  body  and  to  which  the  physiological 
action  of  the  organic  body  is  due.  Examples,  coniine,  C8H15N, 
the  proximate  principle  of  conium  maculatum,  morphine,. 
C17H19NO3,  codeine,  C18H21NO3,  etc.,  proximate  principles  of 
opium. 

Oxygen  is  the  predominating  element  in  inorganic  chemistry, 
carbon  in  organic  chemistry. 

In  organic  chemistry  the  same  laws  of  combination  apply 
as  in  inorganic  chemistry. 

The  belief  that  a  so-called  vital  force  was  a  necessity  in  the 
formation  of  organic  compounds  was  overthrown  in  1828,  by 
Woehler's  synthetical  production  of  urea  from  substances 
considered  inorganic, — namely,  ammonia  and  cyanic  acid  (the 
two  forming  NH4CNO,  ammonium  cyanate). 

NH3  +  HCNO  =  NHjCNO 

By  slowly  heating  NH4CNO,  ammonium  cyanate,  on  a 
water-bath  at  a  temperature  between  50°  C.  and  70°  C.  a  re- 
arrangement of  the  atoms  occurs  with  the  formation  of  urea. 

NH4CNO  —  CO(NH2)2 

Ammonium  cyanate.     •         Urea. 

The  next  organic  compound  produced  synthetically  was 
CN,  cyanogen,  by  Fownes  in  1841.  This  was  produced  by 
passing  nitrogen  over  red-hot  charcoal  (carbon). 

C2  +  N2  =  C2N2 


8  NOTES  ON  CHEMICAL  LECTURES. 

Berthelot  followed  in  1856  by  the  synthetical  production  of 
HCHO2,  formic  acid.  This  was  produced  by  passing  CO, 
carbon  monoxide,  over  heated  KOH,  potassium  hydroxide, 
forming  KCHO2,  potassium  formate.  The  latter  compound 
when  treated  with  HC1  (hydrochloric  acid)  breaks  up  into 
HCHO2,  formic  acid,  and  KC1,  potassium  chloride. 

CO  +  KOH  =  KCHO2 
KCHO2  +  HC1  =  HCHO2  +  KC1 

Wurtz  in  1862  produced  C2H5OH,  ethyl  alcohol,  syntheti- 
cally. The  alkaloid  coniine,  C8H15N,  has  been  produced 
synthetically. 

Thousands  of  organic  compounds  have  been  produced  syn- 
thetically in  the  past  twenty-five  years,  some  of  them  of  the 
greatest  importance ;  for  example,  the  aniline  coloring-matters, 
'indigo,  and  many  of  the  medicines  as  antipyrin,  phenacetin, 
etc.,  now  largely  used  in  medical  practice.  The  number  of 
organic  compounds  produced  synthetically  is  far  greater  than 
those  existing  in  nature. 

It  was  urged  that  the  synthesis  of  urea  was  only  the  pro- 
duction of  a  simpler  substance  from  a  more  complex  one. 
K4Fe(CN)6  having  been  the  complex  substance  used  in  the 
production  of  the  NH4CNO,  ammonium  cyanate,  from  which 
the  urea  was  finally  produced.  This  was  met  by  the  syntheti- 
cal production  of  a  complex  substance,  C21H18N2,  benzalde- 
hyde,  from  a  more  simple  one,  C7H6O,  benzamide,  oil  of  bitter 
almonds.  This  was  effected  by  passing  NH3,  ammoniacal  gas, 
into  C-H6O,  oil  of  bitter  almonds. 

3C7H6O  +  2NH3  =  C21H18N2  +  3H2O 

A  radical  is  a  chemical  combination  of  two  or  more  elements 
capable  of  playing  the  part  of  an  elementary  form  of  matter. 

Behaving  as  an  element,  radicals  must  have  valence  and 
electrical  affinities  corresponding  with  elements.  They  may 
be  monivalent,  divalent,  etc.,  and  either  electro-positive  or 
electro-negative.  As  they  are  unsaturated  molecules  a  neutral 
radical  is  an  impossibility. 

In  1872,  Scheele  recognized  the  compound  Hg(CN)2, 
mercuric  cyanide,  and  in  1815,  Gay-Lussac  isolated  CN,  it 
being  the  first  radical  isolated. 


NOTES  ON  CHEMICAL  LECTURES.  9 

CN  (or  Cy,  which  is  an  abbreviation  of  the  name — cyanogen,) 
may  be  taken  as  the  type  of  the  negative  radicals. 

Cyanogen,  in  combining  with  positive  elements  or  with 
positive  radicals,  may  be  compared  with  the  negative  element 
Cl,  chlorine,  for  example, 

KC1,  also  KCN,  a  simple  salt, — potassium  cyanide. 
AgCl,  also  AgCN,  a  simple  salt, — argentic  cyanide. 
HC1,  also  HCN,  a  hydrogen  acid, — hydrocyanic  acid. 
HC1O,  also  HCNO,  an  oxyacid, — cyanic  acid. 
KC1O,  also  KCNO,  an  oxyacid  salt, — potassium  cyanate. 

CN  therefore  unites  with — 

1.  Hydrogen  to  form  a  hydrogen  acid. 

2.  Metals  to  form  simple  salts. 

3.  Hydrogen  and  oxygen  to  form  an  oxyacid. 

4.  Hydrogen,  oxygen,  and  a  metal  to  form  an  oxyacid  salt. 

A  radical  may  contain  a  metal.  When  KCN,  potassium 
cyanide,  is  heated  with  metallic  iron  in  the  presence  of  air,  a 
radical,  called  ferrocyanogen,  Fe(CN)6,  is  formed. 

6KCN  +  Fe  +  O  =  K4Fe(CN)6  +  K2O 

The  radical  Fe(CN)6  has  never  been  isolated.  Sometimes 
it  is  expressed  FeCy6  or  Cfy.  It  is  a  tetrad  radical.  The  K 
in  K4Fe(CN)6  may  be  replaced  by  H,  forming  H4Fe(CN)6, 
ferrocyanic  acid. 

If  chlorine  be  passed  through  a  solution  of  K4Fe(CN)6,  one 
atom  of  K  is  withdrawn,  and  K0Fe2(CN)J2,  potassium  ferri- 
cyanide,  is  formed. 

2K4Fe(CN)6  +  C12  =  K0Fe2(CN)12  +  2KC1 

The  negative  radical  Fe2(CN)12  is  a  hexad.  It  has  never 
been  isolated.  The  K  in  K6Fe2(CN)12  may  be  replaced  by  H, 
forming  HcFe2(CN)12,  ferricyanic  acid. 

C2H5,  ethyl,  may  be  taken  as  the  type  of  the  positive  organic 
radicals.  Ethyl,  in  combining  with  negative  elements  or  with 
negative  radicals,  may  be  compared  with  the  positive  element 
K,  potassium,  for  example, 


10  NOTES  ON  CHEMICAL  LECTURES. 

KC1,        also  C2H3C1,        ethyl  chloride. 
K2S,  "    (C2H5)2S,      ethyl  sulphide. 

K2O,          "    (C2H5)2O,     ethyl  oxide. 
KHSO4,     "    C2H5HSO4,  ethyl  sulphuric  acid. 
KCN,         "    C2H5CN,      ethyl  cyanide. 
KCNO,      "    C2H5CNO,  ethyl  cyanate. 

C2H5  therefore  unites  with — 

1.  Members  of  the  chlorine  group  to  form  simple  salts. 

2.  Oxygen  to  form  an  oxide. 

3.  An  oxyacid  to  form  an  oxyacid  salt. 

The  first  positive  radical  containing  a  metal  isolated  was 
(CH3)2As,  kakodyl  (alkarsin,  dimethylarsin).  It  is  sometimes 
represented  by  the  abbreviation  Kd.  It  is  a  monad  radical. 
It  has  an  intense  affinity  for  oxygen,  combining  with  it  to  form 
(  (CH3)2As)2O,  kakodyl  oxide,  sometimes  represented  by  the 
abbreviation  Kd2O.  Kakodyl  combines  with  chlorine  to  form 
(CH3)2AsCl,  kakodyl  chloride,  and  CN  to  form  (CH3)2AsCN, 
kakodyl  cyanide. 

Kakodyl  alone  and  in  combination  (except  as  kakodylic 
acid)  is  very  poisonous. 

Kakodyl  when  exposed  to  the  air  in  the  presence  of  water 
forms  (CH3)2AsOOH,  kakodylic  acid,  sometimes  abbreviated 
to  HKdO2. 

Kakodylic  acid  contains  54  per  cent  of  metallic  arsenic, 
equivalent  to  71.4  per  cent  of  As2O3,  arsenious  oxide,  but  is 
not  poisonous.  It  is  the  only  kakodyl  compound  that  is  not 
poisonous. 

Kakodyl,  in  combining  with  negative  elements  or  with  posi- 
tive radicals,  may  be  compared  with  K,  for  example, 

KC1,      also  (CH3)2AsCl,          kakodyl  chloride. 
K2O,        "    ( (CH3)2As)2O,      kakodyl  oxide. 
K2SO4,     "    ( (CH3)2As)2SO4,  kakodyl  sulphate. 

(CH3)2As,  kakodyl,  therefore  unites  with — 

1.  Members  of  the  chlorine  group  to  form  simple  salts. 

2.  Oxygen  to  form  an  oxide. 

3.  An  oxyacid  to  form  an  oxysalt. 


NOTES  ON  CHEMICAL  LECTURES.  11 

There  are  similar  methyl  compounds  of  antimony  and  of 
zinc. 

In  addition  to  (CH3)2As,  dimethylarsin,  there  also  exist, 

CH3As,  monomethylarsin. 
(CH3)3As,  trimethylarsin. 

CH4,  methane,  may  be  considered  a  type  of  the  saturated 
organic  compounds.  All  of  the  carbon  bonds  are  satisfied, 
and  it  is  therefore  a  saturated  molecule.  One,  two,  three,  or 
all  four  atoms  of  H  in  CH4  may  be  replaced  by  certain  other 
elements.  The  radical  remaining  after  the  withdrawal  of  each 
atom  of  hydrogen  has  a  valence  corresponding  to  the  number 
of  hydrogen  atoms  withdrawn. 

1.  CH4  —  H  =  CH3  (methyl),     univalent. 

2.  CH4  —  H2  =  CH2  (methene),  bivalent. 

3.  CH4  —  H3  —  CH  (formyl),     trivalent. 

4.  CH4  —  H4  =  C       (carbon),     quadrivalent. 

Thus  replacing  the  H  by  Cl  we  have — 

1.  CH4  +  2C1  =  CH3C1  +  HC1. 

2.  CH4  +  4C1  =  CH2C12  +  2HC1. 

3.  CH4  +  6C1  ==  CHC13  (chloroform)  +  3HC1. 

4.  CH4  +  8C1  ==  CC14  +  4HC1. 

Or  replacing  the  H  by  iodine  we  have — 

1.  CH4  +  2I  =  CH3I  +  HI. 

2.  CH4  +  41  =  CH2I2  +  2HI. 

3.  CH4  +  61  =  CHI3  (iodoform)  +  3HI. 

4.  CH4  +  81  =  CI4  +  4HI. 

A  type  is  a  form  of  chemical  combination  common  to  a  class 
of  compounds. 

NaCl,  CH3C1,  types  of  simple  salts. 
K2SO4,  (C2H5)2SO4,  types  of  oxysalts. 
H2O,  (C2H5)2O,  the  water  type. 
NH3,  the  ammonia  type. 

By  substitution  is  meant  the  replacing  of  one  or  more  ele- 
ments or  radicals  in  a  compound  by  one  or  more  elements  or 
radicals  without  changing  the  type  of  the  compound. 


12  NOTES  ON  CHEMICAL  LECTURES. 

When  chemical  combination  occurs  it  does  not  necessarily 
follow  that  substitution  has  taken  place. 

Alcohols  and  ethers  may  be  viewed  as  substitution  com- 
pounds. 

An  alcohol  may  be  considered  after  the  type  of  water,  in 
which  one  atom  of  H  in  H2O  has  been  replaced  by  an  alcohol 
radical,  as 

H  OH,  water. 
C2H5OH,  ethyl  alcohol. 

An  ether  may  be  considered  after  the  type  of  water,  in 
which  both  atoms  of  H  in  H2O  have  been  replaced  by  alcohol 
radicals,  as 

H2O,  water. 
(C2H5)2O,  ethyl  ether. 

EXAMPLES  OF  SUBSTITUTION. 

When  HgCl2,  mercuric  chloride,  is  treated  with  NH3,  ammo- 
niacal  gas,  one  of  the  atoms  of  Cl  in  the  HgCl2  is  replaced  by 
the  amido-radical  NH2,  and  HgNH3Cl,  amido-mercuric  chloride 
(white  precipitate),  is  formed. 

HgCl2  +  2NH3  =  HgNH2Cl  +NH4C1 

When  Hg2Cl2,  mercurous  chloride,  is  treated  with  NH3,  am- 
monia, one  of  the  atoms  of  Cl  in  the  Hg2Cl2  is  replaced  by  the 
amido-radical  NH2,  and  Hg2NH2Cl,  amido-mercurous  chloride 
(black  precipitate),  is  formed. 

Hg2Cl2  +  2NH3  =  Hg2NH2Cl  +  NH4C1 

HgNH2Cl  and  Hg2NH2Cl  are  inorganic  substitution  com- 
pounds after  the  type  of  NH4C1,  ammonium  chloride,  in  which 
two  hydrogen  atoms  have  been  substituted  by  mercury. 

One,  two,  or  all  three  atoms  of  H  in  NH3  may  be  replaced 
by  other  elements  or  radicals. 

An  amide  may  be  defined  as  a  substitution  compound  in 
which  the  hydrogen  of  NH3  has  been  partly  or  wholly  replaced 
by  an  alcohol  radical  or  a  metal. 

Amides  may  unite  with  an  acid  without  replacing  the  hydro- 
gen of  the  acid,  as  in  N(CH3)3HC1  trimethylamide  hydro- 
chloride. 


NOTES  ON  CHEMICAL  LECTURES.  13 

An  amide  may  be  a  constituent  of  a  double  salt,  as  in 
N(CH3)4CNAgCN  tetramethylargentammonium  cyanide. 

We  may  have  NH2K,  potass-amide,  produced  by  the  re- 
placement of  one  atom  of  H  in  NH3  by  K.  By  the  replace- 
ment of  H  in  NH3  by  radicals  we  may  have 

NH2CH3,  methylamide. 

NHCH3C2H5,       methyl-ethylamide. 
NCH3C2H-C3H7,  methyl-ethyl-propylamide. 
NHCH3CH3,        dimethylamide. 
NCH3CH3CH3,    trimethylamide. 

All  the  atoms  of  hydrogen  in  a  compound  are  not  neces- 
sarily replaceable.  For  example,  only  one  atom  of  hydrogen 
in  HC2H3O2,  acetic  acid,  is  replaceable. 

When  C6H10O5,  cellulose  (cotton),  is  treated  with  nitric  acid, 
three  atoms  of  hydrogen  in  the  cellulose  are  replaced  by 
the  NO2,  nitro  radical,  forming  the  explosive  compound 
C6Hr(NO2)3O5,  trinitrocellulose  (gun-cotton). 

C6H1005  +  3HN03  =  C6H7(N02)305  +  3H2O 

When  C3H8O3,  glycerine,  is  treated  with  nitric  acid,  three 
atoms  of  hydrogen  in  the  glycerine  are  replaced  by  the  NO2, 
nitro  radical,  forming  the  explosive  compound  C3H5(NO2)3O3, 
trinitro glycerine. 

C3H8O3  +  3HNO3  =  C3H5(NO2)3O3  +  3H2O 

The  hypothetical  H2CO3,  carbonic  acid,  is  dibasic ;  has  two 
replaceable  atoms  of  hydrogen. 

/  OH 

C  =  O    ,  carbonic  acid. 
\  OH 

By  replacing  one  of  the  OH  hydroxyl  groups  in  carbonic 
acid  by  NH2,  an  amido-acid,  carbamic  acid  is  obtained. 

/  OH 

C  =  O    ,  carbamic  acid. 
\NH2 


14  NOTES  ON  CHEMICAL  LECTURES. 

Carbamic  acid  is  not  known  in  its  free  state.  It  is  always 
in  combination  as  a  salt  or  an  ether.  The  ammonium  salt  is 
produced  by  bringing  together  dry  CO2,  carbon  dioxide,  and 
dry  NH3,  ammoniacal  gas. 

CO2  +  2NH3  =  CO(ONH4)(NH2)  or  NH4NH2CO2,  ammo- 
nium carbamate. 

/  ONH4 

C  =  O       ,  ammonium  carbamate. 
\  NH2 

When  treated  with  water  it  decomposes  into  ammonium 
carbonate. 

CO(ONH4)(NH2)  +  H2O  =  (NH4)2CO3 

Ammonium  carbamate.  Ammonium  carbonate. 

The  ethers  of  carbamic  acid  are  called  urethans.  They 
are  formed  by  replacing  the  atom  of  hydrogen  in  the  remain- 
ing OH  hydroxyl  group  in  CONH2OH,  carbamic  acid,  by 
an  alcohol  radical. 

/  OCH3 

C  —  O       ,  methyl  urethan. 
\  NH2 

/  OC2H5 

C  =  O        ,  ethyl  urethan. 
\  NH2 

Ethyl  urethan  under  the  name  of  "  urethan "  is  used  in 
medicine. 

By  replacing  both  of  the  hydroxyl  groups  in  H2CO3,  car- 
bonic acid,  by  NH2,  an  amide  is  formed,  CO(NH2)2,  carbamide, 
urea. 

/  NH2 

C  =  O     ,  carbamide  (urea). 
\  NH2 

Antipyrin,  phenyldimethyl  pyrazolon,  CnH12N2O,  or 
(C3H(CH3)2N2(C6H5)O),  is  a  substitution  product. 

The  aniline  coloring-matters  are  also  substitution  products. 


<V-   372 


I  lit  67  3'  7  2  - 


-.-?  A 


NOTES  ON  CHEMICAL  LECTURES.  15 

The  composition  of  organic  compounds  may  be  ex- 
pressed by — 

1.  Empirical  formula. 

2.  Molecular  formula. 

3.  Rational  formula. 

4.  Graphic  formula. 

1.  Empirical  formula :    The  simplest  possible  expression 
by  formula  of  the  composition  of  a  compound.     It  indicates 
simply  the  elements  that  enter  into  the  composition  of  the 
compound   in   their  least   atomic  proportions.     Thus  CH2O 
for  acetic  acid. 

An  empirical  formula  may  be  deduced  from  the  results  of  a 
quantitative  analysis  of  a  compound. 

2.  Molecular  formula :  A  formula  that  expresses  a  quantity 
of  a  compound  by  weight  twice  its  specific  gravity  in  the 
gaseous  state  compared  with  hydrogen. 

Or :  A  quantity  of  a  compound  by  weight  in  the  gaseous 
state  twice  the  volume  of  the  atom  of  hydrogen.  Hence  all 
molecules  must  be  of  the  same  size. 

A  molecular  formula  may  be  determined  : 

a.  By  determining  the  specific  gravity  of  the  compound  in 
the  gaseous  state. 

Victor  Meyer's  method;  Depends  on  the  vaporization  of 
a  weighed  quantity  of  a  compound  and  measuring,  by  means 
of  a  eudiometer,  the  volume  of  air  the  vapor  displaces  in  the 
apparatus,  correcting  for  temperature  and  pressure,  and  com- 
paring the  volume  of  air  displaced  with  the  volume  occupied 
by  a  quantity  of  hydrogen  equal  to  the  weight  of  the  com- 
pound volatilized. 

The  molecular  weight  of  a  compound  which  undergoes 
decomposition  before  its  point  of  vaporization  is  reached  cannot 
be  determined  by  this  method. 

Method  :  A  substance  having  a  fixed  boiling-point  is  placed 
in  the  outer  large  glass  tube  of  the  apparatus.  For  compounds 
having  a  low  vaporizing-point  water  may  be  used.  Generally 
(C6H5)2NH,  diphenylamine,  having  a  boiling-point  of  310°  C.,  is 
employed.  Melted  lead  may  be  used  for  compounds  having  a 
higher  vaporizing-point.  The  smaller  bulbed  glass  tube  having 


16  NOTES  ON  CHEMICAL  LECTURES. 

a  curved  delivery-tube  attached  is  lowered  into  the  larger  glass 
tube  until  the  bulbed  end  is  a  few  inches  above  the  surface  of 
the  substance  having  a  fixed  boiling-point.  A  small  quantity 
of  the  compound,  of  which  the  molecular  weight  is  to  be 
determined,  is  weighed  off  in  a  very  small  glass  tube,  which 
is  closed  at  one  end.  The  tube  containing  the  compound  is 
placed  with  the  opening  upward  in  a  perforation  in  the  cork 
of  the  smaller  bulbed  tube,  where  it  is  held  in  place  by  a  wire 
thumb-screw  contrivance,  and  the  cork  thus  arranged  placed 
in  the  smaller  bulbed  tube.  Gentle  heat  is  applied  to  the  outer 
large  tube,  and  gradually  increased  until  the  substance  with 
the  fixed  boiling-point  boils.  After  boiling  a  few  minutes  and 
the  vapor  of  the  boiling  material  reaches  and  is  condensed  to 
a  liquid  at  a  point  opposite  the  bulb  of  the  smaller  glass  tube, 
the  delivery-tube  is  adjusted  so  that  the  exit  is  below  the  sur- 
face of  water  contained  in  a  suitable  vessel.  When  bubbles 
of  air  cease  to  ascend  through  the  water  (at  the  same  time 
the  heating  of  the  material  having  a  fixed  boiling  point  is  kept 
up  so  that  it  is  boiling),  a  eudiometer  filled  with  water  is 
inverted  over  the  exit  of  the  delivery-tube  under  water,  and 
by  turning  the  thumb-screw  contrivance  the  tube  containing 
the  compound  under  examination  is  allowed  to  drop  to  the 
bottom  of  the  inner  bulbed  tube.  (To  break  the  fall  of  the 
tube  containing  the  compound  it  is  customary  to  previously 
place  pieces  of  broken  glass  tubing  in  the  bottom  of  the 
bulb  of  the  inner  glass  tube.) 

Volatilization  of  the  compound  immediately  occurs,  and  a 
volume  of  air  is  displaced  and  collected  in  the  eudiometer 
exactly  equivalent  to  the  gaseous  volume  furnished  by  the 
weight  of  the  compound  volatilized.  This  final  part  of  the 
operation  requires  but  a  few  minutes. 

When  bubbles  of  air  cease  to  come  over,  the  cork  is  taken 
out  of  the  apparatus  and  the  eudiometer  cautiously  removed 
and  placed  in  a  vessel  containing  water.  After  a  time  the  air 
in  the  eudiometer  becomes  of  the  same  temperature  as  the 
water  surrounding  it.  The  volume  of  air  is  now  read  off,  the 
temperature  of  the  water  surrounding  the  eudiometer  and  the 
barometric  pressure  are  observed,  and  the  necessary  calcula- 
tions performed. 


NOTES  ON  CHEMICAL  LECTURES.  17 

Suppose  0.010  gramme  acetic  acid  were  volatilized  and  the 
volume  of  air  displaced  and  collected  in  the  eudiometer 
corrected  for  temperature  (0°  C.)  and  barometric  pressure 
(7GO  mm.),  measured  3.72  c.c. 

0.0 10  gramme  hydrogen  at  0°  C.  temperature  and  760  mm. 
pressure  measure  111.6  c.c. 

Then  111.6-^3.72  =  30 

showing  the  vapor  of  acetic  acid  to  be  30  times  more  dense, 
volume  for  volume,  than  hydrogen. 

c.c.  H.       Gnn.  H.        c.c.  H.  Grm.H. 

Or  11160    :    1    ::    3.72    :    0.00^3 

All  molecules,  elementary  or  compound,  must  be  equal  in 
volume  to  the  volume  occupied  by  the  molecule  of  hydrogen, 
— /.  e.,  twice  the  atomic  volume. 

If  30  grammes  of  acetic  acid  in  the  form  of  vapor  will 
occupy  the  same  volume  as  the  atomic  volume  of  hydrogen, — 
namely,  11160  c.c., — then  60  grammes  of  acetic  acid  will 
occupy  twice  the  atomic  volume,  or  the  molecular  volume  of 
hydrogen, — namely,  22320  c.c. 

A  formula  for  acetic  acid  representing  30  as  its  molecular 
weight  would  be  CH2O  =  30,  really  its  empirical  formula,  and 
expresses  a  quantity  in  the  gaseous  state  equal  to  its  specific 
gravity  compared  with  hydrogen.  By  multiplying  the  30  by 
2  =  60,  we  have  a  number  representing  its  molecular  weight. 
A  formula  for  the  acid  constructed  to  represent  this  number 
would  be  C2H4O2  =  60, — i.e.,  a  formula  that  expresses  a  quan- 
tity by  weight  of  the  compound  twice  its  specific  gravity  in  the 
gaseous  state  compared  with  hydrogen. 

b.  The  molecular  weight  of  an  organic  compound,  especially 
those  compounds  which  are  not  vaporizable,  may  be  deter- 
mined,— 

1.  If  an  acid,  by  combining  it  with  a  metal  to  form  a  salt 
and  determining  the  quantity  of  the  metal  in  combination  in  a 
given  quantity  of  the  salt 

2.  If  a  basic  substance,  by  combining  it  with   an   acid  and 
determining  the  quantity  of  acid   in  combination   in   a  given 
quantity  of  the  salt. 


18  NOTES  ON  CHEMICAL  LECTURES. 

The  molecular  formula  of  many  compounds  which  will  not 
vaporize  or  form  salts  is  determined  by  analyzing  their  sub- 
stitution products. 

The  molecular  formula  of  some  compounds  which  will  not 
vaporize,  form  salts  or  substitution  products,  is  not  definitely 
known,  as  cane-sugar,  starch. 

For  example,  the  molecular  formula  of  acetic  acid,  which 
forms  a  salt  with  silver,  may  be  determined  by  estimating  the 
quantity  of  metallic  silver  in  its  silver  salt. 

Suppose  ].0  gramme  of  argentic  acetate  be  placed  in  a 
crucible  and  heated  until  all  the  organic  matter  is  driven  off 
and  nothing  remains  but  metallic  silver.  After  cooling,  the 
silver  is  weighed. 

Quantity  of  argentic  acetate  taken 1.0000  grm. 

Weight  of  resulting  metallic  silver 0.6468     " 

Quantity  of  organic  compound  C,  H,  and  O,  which 

must  have  been  in  combination  with  the  silver  0.3532     " 

Then 

At.  wt.  of  silver. 

0.6468  :  0.3532  :  :  108  :  58.98  =  C,  H,  and  O,  in  combina- 
tion with  one  atom  of  silver. 


Acetic  acid  is  a  monobasic  acid, — i.  e.,  having  one  replaceable 
atom  of  hydrogen.  Consequently,  as  silver  is  a  monad,  it 
would  take  the  place  of  one  atom  of  hydrogen  in  the  mol- 
ecule of  acid.  Add  1  to  58.98  =  59.98,  and  allowing  for-error 
in  analysis,  say  60.0.  A  formula  constructed  to  equal  that 
number  would  be  C2H4O2  =  60,  acetic  acid. 

The  formula  of  the  silver  salt  is  AgC2H3O2. 

A  recent  method  for  determining  molecular  weight  is  based 
upon  the  observations  of  Raoult  (1883), — namely,  that  the 
lowering  of  tlie  freezing  point  of  a  solution  is  proportional  to 
the  absolute  quantity  of  substance  in  solution  and  inversely  as 
its  molecular  weight.  (Law  of  Raoult.) 

Beckmann's  method  of  determining  the  molecular  weight 
of  a  compound  by  the  depression  of  the  freezing  point  of 


NOTES  ON  CHEMICAL  LECTURES.  19 

the  solvent  employed,  according  to  the  Law  of  Raoult,  is  as 
follows : 

15  to  20  grammes  of  the  solvent,  accurately  weighed,  are 
placed  in  a  hard  glass  tube  2  to  3  centimetres  in  width,  having 
a  tube  projecting  from  the  side,  and  closed  with  a  perforated 
cork,  through  which  are  passed  an  accurately  standardized 
thermometer  (Waldferdin  Thermometer)  and  a  stout  platinum 
wire  which  serves  as  a  stirring  rod.  This  tube  is  then  fixed 
to  the  depth  of  the  side-projecting  tube  in  a  cork  fitted  to  a 
larger  and  wider  tube.  The  latter  serves  as  an  air  jacket. 
The  entire  apparatus  consisting  of  one  tube  inserted  in  another 
is  fixed  in  an  aperture  in  the  cover  of  a  large  glass  vessel 
which  contains  a  freezing  mixture.  The  congealing  point  of 
the  solvent  is  first  determined  by  cooling  it  1°  to  2°  below  its 
freezing  point  and  then  by  agitation  with  the  platinum  wire 
(after  having  added  platinum  clippings)  inducing  the  formation 
of  crystals.  During  this  operation  the  temperature  rises  and 
when  the  mercury  in  the  thermometer  is  stationary  it  indicates 
the  freezing  point  of  the  solvent.  The  mass  of  crystals  is 
permitted  to  melt  and  an  accurately  weighed  quantity  of  the 
compound,  the  molecular  weight  of  which  is  to  be  determined, 
is  introduced  through  the  side-projecting  tube.  When  the 
compound  introduced  is  completely  dissolved  the  freezing 
point  of  the  solution  is  determined  after  the  manner  just 
described. 

Rule    for  calculating  results    in  Beckmann's  method; 

Multiply  the  percentage  of  compound  in  solution  by  the  con- 
stant T  of  the  solvent  employed  and  divide  by  the  depression 
of  the  freezing  point. 

The  solvents  usually  employed  in  Beckmann's  method  are 
water,  benzol  and  glacial  acetic  acid. 

The  constant  T  of  the  solvents  is  as  follows : 

Water 19.0 

Benzol 4.9 

Glacial  acetic  acid   .  39.0 


20  NOTES  ON  CHEMICAL  LECTURES. 

Example  of  determination  of  molecular  weight  of  a 
compound  by  Beckmann's  method: 

Example :  Suppose  a  definite  weight  of  oxyberberine 
acetate  (C20H17NO5HC2H3O2  molec.  wt.  411)  is  employed  and 
glacial  acetic  acid  is  used  as  the  solvent. 

1.573  grms.  oxyberberine  acetate  employed. 
100.400  grms.  glacial  acetic  acid  employed. 

Hence  100.4  :  1.573  :  :  100  :  1.56  grms.  (percentage  of 
oxyberberine  acetate  in  the  solvent). 

Freezing  point  of  glacial  acetic  acid =  16.262°  C. 

Freezing  point  of  glacial  acetic  acid  containing 

the  oxyberberine  acetate =  16.112°  C. 

Depression  of  the  freezing  point :  0.150°  C. 

Therefore, 

39  X  07T50  ==  0.15Q    =  407  molecular  weight 
of  oxyberberine  acetates  from  which  the  molecular  formula 
is  constructed. 

The  molecular  formula  of  many  substances  which  before 
the  introduction  of  Beckmann's  method  could  not  be  accurately 
determined,  are  now  determined  with  accuracy  by  this  method. 
Example,  glucose. 

3.  A  rational  formula  attempts  to  express  the  arrangement 
of  the  atoms  or  groups  of  atoms  in  the  molecule  of  a  com- 
pound. 

The  same  compound  may  be  represented  by  various  rational 
formulas,  depending  on  the  views  of  different  chemists, — e.  g,, 
over  twenty  rational  formulas  have  been  suggested  for  acetic 
acid. 

4.  A  graphic  formula  attempts  to  express  the  arrangement 
of  the  atoms  or  groups  of  atoms  in  the  molecule  of  a  com- 
pound by  means  of  lines  (pictures). 

Acetic  acid. 

Empirical  formula,  CH2O 

Molecular  C,H4O2 

Rational  "        HC2H3O2  or  CH3COOH 


, 


W       0 


J- 


' 


rfT  d  X 


NOTES  ON  CHEMICAL   LECTURES.  21 

H 

I 
Graphic  formula,     H  —  C—     — C  —  O  —  H 

H  O 

Benzol  (benzene). 

Empirical  formula,  CH 
Molecular       "         C6H6 

H 

I 
C 

/  ^ 

Graphic  formula,     H  —  C  C  —  H 

(Kekule's  Benzol                ||  | 

ring.)                         H  —  C  C  —  H 

\  // 
C 

I 
H 

All  of  the  atoms  of  hydrogen  in  benzol  are  replaceable. 
The  hydrogen  atoms  in  benzol  may  be  replaced  by  single 
elements,  as  chlorine,  or  iodine,  or  bromine,  or  by  radicals,  or 
all  of  the  hydrogen  may  be  replaced  by  elements  unlike  each 
other  or  by  unlike  radicals. 

By  replacing  the  hydrogen  atoms  in  benzol  with  chlorine 
we  may  have 

C6H5C1,   monochlor  benzol. 

C6H4C12,  dichlor 

C6H3C13,  trichlor 

C6H2C14,  tetrachlor 

C6HC15,  pentachlor       " 

CGC16,       hexa-  or  perchlor  benzol. 

Amido-benzol,  or  aniline,  C6H5NH2,  is  a  compound  formed 
by  replacing  one  of  the  atoms  of  hydrogen  in  benzol  by  the 
NH2,  amido  group. 


22  NOTES  ON  CHEMICAL  LECTURES. 

There  are  three  distinct  isomeric  dinitrobenzols,  (dinitro- 
benzenes).     They  are 

Orthodinitrobenzol. 

Metadinitrobenzol 

Paradinitrobenzol. 

Kekule's  Benzol  ring. 

6/\2 


\/ 

4 


When  the  hydrogen  atoms  at  the  positions  1  and  2  have 
been  replaced,  the  compound  is  termed  an  Ortho  compound. 
Example  : 

N02 

I 
C 

/  ^ 

H  —  C  C  —  NO2 
Orthodinitrobenzol,              ||         | 

H—  C  C—  H 

\    // 
C 

I 
H 

When  the  hydrogen  atoms  at  the  positions  1  and  3  have 
been  replaced,  the  compound  is  termed  a  Meta  compound. 
Example  : 

NO, 

I 
C 

/  ^ 

H—  C  C—  H 
Metadinitrobenzol,                 ||         | 

H  -  C  C  -  N02 

\    // 
C 


H 


NOTES  ON  CHEMICAL  LECTURES.  23 

When  the  hydrogen  atoms  at  the  positions  1  and  4  have 
been  replaced,  the  compound  is  termed  a  Para  compound. 
Example : 

NO2 

I 
C 

/  ^ 

H  —  C  C  — H 
Paradinitrobenzol, 

H  — C  C—  H 

\    // 

C 

I 
N02 

Phenol,  or  carbolic  acid,  C6H5OH,  may  be  produced  by 
replacing  one  of  the  hydrogen  atoms  in  benzol  by  the  OH, 
hydroxyl  group. 

Phenol  is  eliminated  in  the  urine  as  C6H5HSO4,  phenol- 
sulphuric  acid,  or  in  combination  as  a  salt,  C6H5KSO4,  phenol- 
potassium  sulphate.  Phenol  (carbolic  acid)  is  poisonous,  but 
the  salts  of  phenol-sulphuric  acid  are  not  poisonous.  Sodium 
sulphate,  or  magnesium  sulphate  is  recommended  as  an  anti- 
dote in  carbolic  acid  poisoning,  converting  the  acid  into  the 
non-poisonous  salt  phenol-sodium  sulphate,  or  phenol-magne- 
sium sulphate. 

Precipitation  of  barium  as  barium  sulphate  does  not  occur 
on  the  addition  of  barium  chloride  to  a  solution  of  the  salts 
of  phenol-sulphuric  acid.  Thus,  from  the  amount  of  precipitate 
of  barium  sulphate  obtained  on  the  addition  of  barium  chloride 
to  the  urine,  after  the  ingestion  of  carbolic  acid,  it  appears 
that  the  quantity  of  sulphuric  acid  is  diminished,  whereas  it 
really  is  unchanged  or  perhaps  increased. 

Phenol  cannot  be  detected  directly  in  the  urine  by  any  of 
the  tests.  It  must  first  be  liberated  from  its  combination  as 
phenol-sulphuric  acid,  distilled,  the  distillate  agitated  with  ethyl 
ether,  the  ethyl  ether  allowed  to  separate  and  then  removed 
from  the  aqueous  solution  and  allowed  to  evaporate.  The 
residue  is  dissolved  in  a  small  quantity  of  water  and  the  tests 
for  phenol  applied. 


24  NOTES  ON  CHEMICAL  LECTURES. 

Detection  of  phenol  in  the  urine. — 25  c.c.  of  sulphuric 
acid  are  added  to  500  c.c.  of  the  urine,  the  mixture  is  distilled 
until  bromine  water  added  to  a  part  of  the  last  portion  of  the 
distillate  fails  to  produce  a  turbidity.  The  distillate  is  agitated 
with  ethyl  ether,  after  the  ether  has  separated  from  the  water, 
it  is  removed  with  a  pipette,  and  allowed  to  evaporate.  The 
residue  is  dissolved  in  a  small  quantity  of  water  and  the  tests 
for  phenol  are  applied. 

On  the  addition  of  a  dilute  neutral  solution  of  ferric  chloride 
to  an  aqueous  solution  of  phenol  (carbolic  acid)  an  intense 
purple  color  is  produced. 

On  the  addition  of  bromine  water  to  an  aqueous  solution  of 
phenol  until  a  permanent  yellowish  coloration  is  produced,  a 
yellowish  white,  crystalline  precipitate  of  C6H2Br3OH,  tribrom- 
phenol  is  formed.  If  the  dilution  is  1  to  40,000  the  turbid- 
ity appears  immediately,  if  the  dilution  is  1  to  50,000  a 
crystalline  precipitate  appears  only  after  the  solution  has  stood 
several  hours. 

Isomerism  is  a  term  applied  to  bodies  containing  the  same 
elements  united  in  the  same  relative  proportions  by  weight, 
but  differing  more  or  less  widely  in  their  physical,  physio- 
logical, and  chemical  properties. 

The  first  isomeric  compounds  discovered  were 

CH4,  methane. 
CH4,  attar  of  roses. 

Isomeric  compounds  are  of  two  classes. — 1.  Polymeric  : 
Where  the  percentage  composition  is  similar,  but  the  molecular 
composition  dissimilar, — /.  e.,  the  same  empirical  but  different 
molecular  formula. 

The  olefines  are  examples  of  polymeric  compounds,  as  are 
also  the  cyanogen  oxyacids. 

HCNO,       cyanic  acid,  monobasic. 
H2C2N2O2,  fulminic  acid,  bibasic. 
H3C3N3O3,  fulminuric  acid,  monobasic. 
H3C3N3O3,  cyanuric  acid,  tribasic. 

2.  Metameric:  Where  both  the  percentage  and  the  mole- 
cular compositions  are  alike. 


A    '-   'hAjuZs— 


'  ;  • 

". 


l*~* 


NOTES  ON  CHEMICAL  LECTURES.  25 

The  oils  of  turpentine,  lemons,  bergamot,  cloves,  and  pepper 
are  examples  of  metameric  compounds.      They  all  have  a 
similar  percentage  and  molecular  composition,  C10Hi6. 
C3H6O3,  lactic  acid,  ^ 

C3H6O3,  paralactic  acid,      Vare  metameric. 
C3H6O3,  hydracrylic  acid,  J 

An  homologous  series  is  a  series  of  chemical  compounds 
made  up  of  the  same  elements,  but  having  a  common  differ- 
ence in  their  molecular  formula. 

Hydrocarbons  of  equal  equivalence,  as  CH4,  may  exist 
separately,  whilst  hydrocarbons  of  unequal  equivalence,  as 
CH3,  are  incapable  of  existing  in  the  free  state,  unless,  perhaps, 

CH3 
as  double  molecules, — /.  e.,  \    =    C2H6. 

CH3 
As  examples  of  homologous  series  we  have  the — 

1.  defines. 

2.  Alcohol  radicals. 

3.  Paraffins. 

4.  Alcohols. 

5.  Aldehydes. 

6.  Volatile  fat  acids. 

7.  Ethers. 

In  the  above  homologous  series  the  common  difference  in 
the  molecular  formula  is  CH2. 

1.  defines  :  Diatomic,  polymeric,  hydrocarbon  cormieunds. 
j/      t-  fK~fJi£~4'  *^&3       * 

>v*f      >»U  «^W»rf-^t<yI 

1.  CH2,     methene  (hypothetical) 

2.  C2H4,    ethene 14 

3.  C3H6,    propene 21 

4.  C4H8,    butene 28 

5.  C5H10,  pentene      .    .        35 

6.  C6H12,  hexene 42 

7.  C7HU,  heptene 49 

8.  C8H16,  octene 56 

9.  C9H18,  nonene 63 

10.  QoHaj,  decene 70 

and  continuing  to 

30.   C^H^,  melene,  found  in  wax. 


26  NOTES  ON  CHEMICAL  LECTURES. 

2.  Alcohol  radicals  (may  exist  only  as  double  molecules): 
Olefines  +  one  atom  of  H,  hydrides  of  the  olefines,  mona- 
tomic. 

I    fj+Hz}.  CH3)    methyl. 

2.  C2H5,  ethyl. 

3.  C3H7,  propyl. 

4.  QH9,  butyl. 

5.  C5Hn,  amyl. 

Etc.       <V-^, 

The  alcohol  radicals  form  salts,  as  CH3I,  CH3C1,  etc. 

3.  Paraffins  :  Alcohol  radicals  -f-  one  atom  of  H,  hydrides 
of  the  alcohol  radicals,  saturated  hydrocarbons. 


1.  CH4,    methane. 

2.  C2H6,  ethane. 

3.  C3H8,  propane. 

4.  C4H10,  butane  or  quartane. 

5.  C5H12,  pentane. 

6.  C6H14,  hexane. 


4.  Alcohols,    monatomic   or   monohydric,  ethylic   series  : 

Alcohol  radicals  -f-  OH  (hydroxyl),  may  be  regarded  after 

the  type  of  H2O,  in  which  one  atom  of  H  in  H2O  has  been 
replaced  by  an  alcohol  radical. 


1. 

2. 
3. 
4. 
5. 
6. 

CH3OH, 
C2H5OH, 
C3H7OH, 
QH9OH, 
C5HUOH, 
C6H13OH, 
Etc. 

Vapor  density 
compared  with  I 

methylic  alcohol  (wood  spirit)     .    .  16 
ethylic          "       (ordinary  alcohol)  23 
oroDvlic        "                                      -  30 

Boiling 
1.        point. 

150°  F. 
173° 

205° 
233° 
270° 
305° 

butylic          "        ... 

37 

amylic                   .    .    . 

44 

caprylic        "        ... 

51 

5.  Aldehydes  of  the  acetic  series  (alcohol  dehydrogena- 
tum) :  Alcohols  minus  two  atoms  of  H.  Under  the  influence 
of  oxidizing  agents  alcohols  give  up  two  atoms  of  H,  forming 
aldehydes,— viz.,  CH3OH  +  O  =  CH2O  +  H2O. 


NOTES  ON  CHEMICAL  LECTURES.  27 

1.  CH2O,    mcthylic  or  formic  aldehyde. 

2.  C2H  A   ethylic  or  acetic 

3.  C3H6O,  propylic 

4.  C4HA  butylic 

5.  C3H10O,  valeric 

Etc. 

G.  Fat  acids,  acetic  series :  Aldehydes  +  one  atom  of 
oxygen,  monatomic. 

1.  CH2O2,    formic   acid,  found  in  red  ants. 

2.  C2H4O,,  acetic       "          "      "    vinegar. 

3.  C3H6O,,   propylic  "  "       "    oils. 

4.  C4H8O,,   butyric    "  "       "    rancid  butter. 

5.  C5H10O2,  valeric     "           "       "    valerian. 

6.  QH12O2,  caproic    "          "      "    rancid  butter  and  sweat. 

And  continuing  regularly  to 

20.  CMHWO2,  butic     acid,  found  in  butter. 
30.  C30HWA,  melissic  "         "       "  beeswax. 

7.  Ethers,  of  monohydric  alcohols  ;  Oxides  of  the  alcohol 
radicals,  after  the  type  of  H2O,  in  which  both  atoms  of  H  in 
the  H2O  are  replaced  by  alcohol  radicals. 

1.  (CH3)2O,    methylic  ether. 

2.  (C2H5)A  ethylic 

3.  (C3H-)20,  propylic      " 

4.  (C4H9)2O,  butylic 

5.  (C5Hn)2O,  amylic 

Every  alcohol  has  its  corresponding  aldehyde,  acid,  and 
ether. 

The  paraffins  are  saturated  hydrocarbon  compounds. 

By  replacing  3  atoms  of  H  in  a  paraffin  with  3  hydroxyl 
(OH)  groups  a  triatomic  (trihydric)  alcohol  is  formed. 
Glycerine  (C^H-^OH).,)  is  a  triatomic  alcohol. 

Replacing  3  atoms  of  H  in  the  paraffin  C3H.<,  propane,  with 

OH 
3  hydroxyl   groups,  a  triatomic  alcohol,  C3H-OH  =  C3HAs» 

OH 
glycerine  (propenyl  alcohol),  is  formed. 


28  A'OTES  ON  CHEMICAL  LECTURES. 

Glycerine  occurs  in  most  animal  and  vegetable  fats  in  com- 
bination with  the  acids  of  the  acetic  and  oleic  series, — as 
glycerides.  Suet  contains  stearin,  C3H5(C18H35O2)3,  a  glyceride 
of  stearic  acid. 

By  the  action  of  superheated  steam  on  the  stearin  in  fats 
glycerine  and  stearic  acid  are  set  free. 

QH^H^s  +  3H20  =  C3H5(OH)3  +  SC^O, 

Stearin.  Water.  Glycerine.  Stearic  acid. 

All  the  monatomic  alcohols  of  the  ethylic  series  (the  ordi- 
nary alcohols)  excepting  the  first  two  members  of  the  series 
have  numerous  isomeric  modifications.  They  are  distinguished 
especially  by  their  behavior  on  oxidation.  Kolbe  gave  to 
methylic  alcohol,  CH3OH,  the  name  carbinol,  whilst  all  the 
succeeding  alcohols  of  the  series  he  termed  carbinols,  regard- 
ing them  as  derivatives  of  the  first  term  CH3OH,  methylic 
alcohol,  and  formed  by  the  replacement  of  hydrogen  by  monad 
alcohol  radicals. 

1 .  Primary  alcohols  ;  Compounds  in  which  one  atom  of  H 
of  the  CH3  of  carbinol  (CH3OH)  is  replaced  by  an  alcohol 
radical. 

a.  CH2CH3OH  =  C2H5OH,  methyl  carbinol  (ethylic  alco- 
hol). 

b.  CH2C2Hr>OH  =  C3H-OH,  ethyl   carbinol  (propylic  alco- 
hol). 

Primary  alcohols  on  oxidation  yield — 

1.  An  aldehyde. 

2.  A  fat  acid. 

3.  An  ethereal  salt. 

1.  C2H5OH  +  O  =  C2H4O  +  H2O 

Ethylic  alcohol.  Acetic  aldehyde. 

2.  C2H40  +  O  =  C2H A 

Acetic  aldehyde.  Acetic  acid. 

3.  C2H4O2  +  C2H5OH  =  C2H5C2H3O2  +  H2O  * 

Acetic  acid.         Ethylic  alcohol.  Ethylic  acetate  (acetic  ether) 

2.  Secondary  alcohols :  Compounds  in  which  two  atoms 
of  H  of  the  CH3  of  carbinol  are  replaced  by  alcohol  radicals. 


NOTES  ON  CHEMICAL  LECTURES.  29 

a.  CHCH3CH3OH  =  C3H7OH,  dimethyl  carbinol  (isomeric 
with  propylic  alcohol). 

b.  CHCH,C,H,OH  =  C4H9OH,  ethyl  methyl  carbinol  (iso- 
meric with  butylic  alcohol). 

Secondary  alcohols  on  oxidation  yield — 

1.  No  aldehyde. 

2.  A  ketone. 

3.  An  acid  containing  a  less  number  of  carbon  atoms  than 
the  alcohol  oxidized, — i.e.,  an  acid  of  the  fat  series. 

Ketone  :  An  aldehyde  in  which  one  atom  of  hydrogen  is 
replaced  by  an  alcohol  radical^  ^    Oj-0  ~  H^  0  -+C?  /V,    0 

C2H4O    ±=    C2H3CH3O 

Acetic  aldehyde.  Acetic  ketone. 

3.  Tertiary  alcohols :  Compounds  in  which  three  atoms  of 
H  in  the  CH3  of  carbinol  are  replaced  by  alcohol  radicals. 

a.  CCH,CH3CH3OH  =  QH9OH,  trimethyl   carbinol    (iso- 

CH3 

I 

meric  with    butylic   alcohol),   CH3— C— OH  =  C4H9OH,  tri- 

CH3 

methyl  carbinol  (isomeric  with  butylic  alcohol). 

b.  CCH3CH3C2H5OH  =  C5HUOH,  ethyl  dimethyl  carbinol 
(isomeric  with  amylic  alcohol). 

Tertiary  alcohols  on  oxidation  yield — 

1.  No  aldehyde. 

2.  No  ketone. 

3.  One  or  more  acids  of  the  acetic  series. 

Four  primary  alcohols ; 
Three  secondary  alcohols ; 
One  tertiary  alcohol ; 

are  possible,  having  the  same  empirical  and  molecular  formula. 
Six  of  these  are  well  known,  the  other  two  have  not  yet  been 
discovered. 


30  NOTES  ON  CHEMICAL  LECTURES. 

DECOMPOSITION  OF  ORGANIC  SUBSTANCES. 

All  organic  substances  are  naturally  prone  to  undergo  de- 
composition. If  the  organic  substance  contain  nitrogen,  the 
tendency  towards  decomposition  is  increased. 

DECOMPOSING  AGENTS, 
i.  Oxygen. 

1.  Direct  combustion. 

2.  Slow  combustion  as  in  the  eremacausis  (slow  oxidation) 
of  oak  wood. 

QsH^On  -f  O2  =  2H2O  -f  C18H18OU 

Oak  wood. 

then 

Ci$H,8Ou  =  CO2  +  Cj7H18O9 

/.  e., — as  soon  as  two  atoms  of  oxygen  have  taken  away  four 
atoms  of  hydrogen,  one  atom  of  carbon  unites  with  two  atoms 
of  oxygen,  and  so  on  until  finally  nothing  remains  of  the  oak 
wood  but  carbon.  This  is  sometimes  used  as  an  illustration 
of  the  formation  of  coal. 

3.  When  nitrogen  is  present  in  the  compound,  fermenta- 
tion or  putrefaction   may  take  place.     Ammoniacal  gas,  NH3, 
may  be  given  off. 

Chlorine,  bromine,  and  iodine  may  produce  decomposition. 
New  compounds  are  formed. 

C6H6  +  C12  =  C6H5C1  +  HC1 

Continuing  the  addition  of  chlorine,  all  of  the  hydrogen  in 
C6H6  may  be  replaced,  leaving  C6C16,  hexachlorbenzol  (per- 
chlorbenzol). 

2.  Heat. 

1.  Some  compounds  when  heated  to  a  certain  temperature 
volatilize,  and  when  cooled  sublime  unchanged ;    examples  : 
strychnine,  morphine,  benzoic  acid. 

2.  Other  compounds  when  heated  directly  in  the  air  undergo 
decomposition  (burn).     If  inorganic  matter  be  absent,  no  resi- 
due remains. 


NOTES  ON  CHEMICAL  LECTURES.  31 

3.  When  organic  compounds  are  heated  in  a  closed  vessel 
they  undergo  destructive  distillation,  as  in  the  destructive  dis- 
tillation of  coal  in  the  manufacture  of  illuminating  gas.  Pyro- 
acids  may  be  formed  as  in  the  production  of  pyroligneous  acid 
in  the  destructive  distillation  of  wood. 

3.  Acids. 

1.  Nitric  acid. 

a.  If  the  organic  compound  be  basic,  it  may  combine  with 
it  and  form  a  salt,  as 

C^H^NAHNOg,  strychnine  nitrate. 

b.  It  may  effect  the  oxidation  of  the  organic  compound,  as 

Q.H^On  -f  9O2  =  6H2C2O4  -f  5H2O 

Cane  sugar.  Oxalic  acid. 

c.  It  may  form  substitution  compounds,  as 

C6H8          +     HN03  H20         +       C6H5N02 

Benzol.  Nitrobenzol  (oil  of  mirbane). 

C3HA      +     3HNO3  C3H3(NO2)3O3     +     3H2O 

Glycerine.  Trinitroglycenue. 

C,;H5OH    +     3HNO3     =     C6H2(NO2)3OH  +     3H2O 

Phenol  (carbolic  acid).  Trinitrophenol  (picric  acid). 

2.  Sulphuric  acid. 

a.  If  the  organic  compound  be  basic,  it  may  combine  with 
it  and  form  a  salt,  as 

(C17H19NO3)2H2SO4   -j~  5H2O,  morphine  sulphate. 
(C^H^NA^risO,  +  8H2O,  quinine 

b.  It  may  decompose  the  organic  compound,  as 
CH202     +     H2S04     =     CO     -I-     H20     +     H2S04 

Formic  acid.  Carbon  monoxide. 

c.  It  may  abstract  the  elements  of  water  from  the  organic 
compound,  as 

H2C2O4  +  H2SO4  =  CO2  +  CO  +  H2O  +  H2SO4 

Oxalic  acid. 

d.  It  may  introduce  the  elements  of  water  into  the  organic 
compound  (assimilation  of  the  elements  of  water),  as 

C6H1005  -f  H2S04  +  H20  =  C6H1206  +  H2SO4 

Starch.  Glucose. 


32  NOTES  ON  CHEMICAL  LECTURES. 

The  property  possessed  by  H2SO4  of  converting  starch  into 
glucose  is  made  use  of  in  determining  starch  quantitatively, 
— /.  e.,  converting  the  starch  into  glucose  and  determining  the 
quantity  of  the  latter,  and  calculating  the  amount  of  starch 
from  the  amount  of  glucose  obtained. 

C6H5OH,  phenol  (carbolic  acid),  treated  with  H2SO4  forms 
C,;H5HSO4,  phenol-sulphuric  acid. 

C6H5OH  +  H2SO4  =  C6H5HSO4  +  H2O 

This  acid  (C6H-HSO4)  is  formed  when  carbolic  acid  is  in- 
gested. 

The  salts  of  phenol-sulphuric  acid  are  not  poisonous.  Anti- 
dotes for  carbolic  acid,  sodium  sulphate,  magnesium  sulphate, 
or  any  soluble  non-poisonous  sulphate. 

4.  Alkalies. 

a.  If  the  organic  compound  be  an  acid,  alkalies  will  'com- 
bine with  it  and  form  salts,  as 

H2C2O4  +  2NaOH  ==  Na2C2O4  -f  2H2O 

Ox«lic  acid.  Sodium  oxalate. 

b.  Alkalies  may  cause  combination  of  the  elements  in  a 
compound. 

KOH  -f  CO  =  KCHO2 

Potassium  formate. 

c.  If  the  compound  acted  upon  by  the  alkali  contain  nitro- 
gen directly  combined,  the  nascent  hydrogen  evolved  in  the 
decomposition    combines    with    the    nitrogen    to    form    NH3 
ammonia. 

The  alkaline  substance  usually  employed  is  soda-lime,  com- 
posed of 

One  part     NaOH  (caustic  soda). 
Two  parts  CaO      (caustic  lime). 

PUTREFACTION  AND  FERMENTATION. 

Putrefaction ;  Chemical  decomposition  of  nitrogenous  or- 
ganic compounds,  under  certain  conditions,  by  bacteria,  with 
the  evolution  of  more  or  less  disagreeable  odors. 

Professor  Sir  Henry  Roscoe,  F.  R.  S.,  says,  in  connection 
with  the  causation  of  the  symptoms  in  infectious  diseases,  that 


NOTES  ON  CHEMICAL  LECTURES.  33 

"  the  symptoms  of  infectious  diseases  are  no  more  due  to  the 
microbes  which  constitute  the  infection  than  alcoholic  intoxi- 
cation is  produced  by  the  yeast-cell,  but  these  symptoms  are 
due  to  the  presence  of  definite  chemical  compounds,  the  result  of 
the  life  of  these  microscopic  organisms." 

Fermentation  :  Decomposition  of  certain  non-nitrogenous 
organic  compounds  in  the  presence  of  certain  nitrogenized 
substances  known  as  fermentation  fungi. 

Ferment  :  A  nitrogenous  body  capable  of  inducing  fermen- 
tation in  a  non-nitrogenous  body.  The  yeast-cell  is  an 
example  of  a  ferment. 

Ordinary  yeast  is  composed  principally  of  two  varieties  of 
cells,  — 

Torula  cerevisiae  (large  round  cells). 
Penicilium  glaucum  (small  oval  cells). 

Fermentescible  body  :  A  non-nitrogenous  body  capable 
of  undergoing  fermentation.  Glucose  is  an  example  of  a 
fermentescible  bod^^  ^  f^^  ,  (J^u^  tuw 

Amygdalin,  aJferrnentesciDle  body,  is'broken  $p  by  emu/sin, 
a  ferment  (both  being  constituents  of  bitter  almonds,  peach- 
kernels,  etc.),  into 


+    2H20    :   :    C7H60     +     HCN    +    2C6H12O6 

Amygdalin.  Oil  of  bitter  almonds.     Hydrocyanic  acid.  Glucose. 

Certain  conditions  are  necessary  in  a  fermentation,  — 

viz.,  the  presence  of  a  ferment,  a  fermentescible  body,  and 
moisture,  a  certain  temperature,  20°  to  40°  C.  (70°  to  100°  F.). 
Air  must  be  present,  at  least  at  the  beginning  of  the  fermenta- 
tion. The  presence  of  a  small  quantity  of  salts  of  the  alkaline 
earths  facilitates  the  progress  of  fermentation. 

Fermentation  may  be  prevented  by  metallic  salts,  as  HgCl2, 
CuSO4,  etc.,  a  temperature  above  100°  F.  and  below  70°  F. 

There  are  five  varieties  of  fermentation,  their  distinctive 
names  being  derived  from  the  principal  product  furnished  : 

1  .  Alcoholic,  or  vinous,  in  which  alcohol  is  produced. 

2.  Acetous,  "       "      acetic  acid 

3.  Lactic,  "       "      lactic  acid 

4.  Butyric,  "       "      butyric  acid  " 

5.  Viscous,  "       "      a  gummy  matter  " 


34  NO  TES  ON  CHEMICAL  LECTURES. 

1.  Alcoholic  fermentation  is  fermentation  characterized  by 
the  formation  of  alcohol.     It  results  from  the  action  of  yeast 
on  a  solution  of  glucose.     The  active  agent  or  ferment  is  the 
torula  cerevisice  of  the  yeast.     Only  95  per  cent,  of  the  glucose 
is  fermented.     The  remaining  five  per  cent,  is  converted  into 
aldehydes,  fat  acids  and  perhaps  other  alcohols. 

1  molecule.  2  molecules.  2  molecules. 

180.  2  X  46  =  92.  2  X  44  =  88. 

C6H12O6   :  :   2C2H5OH    +    2CO2 

Glucose.  Ethyl  alcohol.  Carbon  dioxide. 

Advantage  is  taken  of  this  action  to  determine  the  quantity 
of  glucose  in  urine. 

When  the  alcohol  in  the  solution  reaches  20  per  cent.,  fer- 
mentation ceases.  A  solution  containing  25  per  cent,  of  glucose 
will  not  undergo  fermentation. 

2.  Acetous  fermentation  is  fermentation  characterized  by 
the  formation  of  acetic  acid.     It  is  an  advanced  stage  of  the 
alcoholic  fermentation.     The  active  agent  or  ferment  is  the 
mycodermce  aceti.     It  appears  to  act  as  a  carrier  of  oxygen. 

C2H5OH  +  02  =  C2H402  +  H20 

Ethyl  alcohol.  Acetic  acid. 

3.  Lactic  acid  fermentation  is  fermentation-  characterized 
by  the  formation  of  lactic  acid.     It  results  from  the  action  of 
putrefying  cheese  or  milk  on  glucose  or  milk  sugar.     The 
active  agent  or  ferment  is  the  penicilium  glaucum. 

CuN^Ou  +  H20  =  4C3H603 

Milk  sugar.  Lactic  acid. 

C6H12O6  =  2C3H6O3 

Glucose  Lactic  acid. 

Milk  sugar  and  lactose  C^H^On  +  H2O  are  synonymous  terms 
for  the  same  compound.  Galactose,  C6H12O6,  is  derived  from 
milk  sugar.  It  results  from  boiling  milk  sugar  with  dilute 
sulphuric  acid. 

4.  Butyric  acid  fermentation  is  fermentation  characterized 
by  the  formation  of  butyric  acid.     It  is  an  advanced  stage  of 
the   lactic   acid  fermentation.     The  ferment  is  the  penicilium 
glaucum,  the  same  as  in  lactic  acid  fermentation. 

2C3H603  =  C4H802  +  2C02  +  2H2 

Lactic  acid.          Butyric  acid. 


(J 


NOTES  ON  CHEMICAL  LECTURES.  35 

5.  Viscous  fermentation  is  a  fermentation  characterized  by 
the  formation  of  gummy  matters.  It  occurs  in  the  fermenta- 
tion of  the  juice  of  the  sugar-beet,  and  also  in  sweet  white 
wines,  the  liquid  becoming  "  ropy."  It  may  be  arrested  by 
the  addition  of  a  little  alum  or  calcium  sulphite.  It  does  not 
occur  in  red  wines  because  of  the  presence  of  astringent  sub- 
stances. The  particular  ferment  causing  this  fermentation  is 
unknown. 

ORGANIC  ANALYSIS. 

PROXIMATE  AND  ULTIMATE. 

Proximate  analysis :  The  separation  and  determination 
of  the  organic  compounds  contained  in  an  organic  body,  as 
the  separation  of  morphine,  etc.,  from  opium. 

Ultimate  analysis :  The  detection  and  determination  of 
the  ultimate  elements  entering  into  the  composition  of  an 
organic  compound,  as  the  quantity  of  C,  H,  O,  and  N  in 
morphine. 

That  the  compound  is  organic  may  be  shown  by  heating  it 
on  platinum  foil ;  if  it  chars  it  is  organic.  Some  compounds 
volatilize  before  the  temperature  of  the  charring-point  is 
reached,  and  others  undergo  decomposition  without  charring. 
Such  compounds  must  be  heated  in  a  sealed  glass  tube  or 
with  cupric  oxide.  If  CO2  or  H2O  are  given  off  when  the 
compound  is  heated  with  cupric  oxide  it  is  organic. 

Organic  compounds  may  be  composed  of  C  and  H  or  C  and 
N ;  C,  H,  and  O  ;  C,  H,  N,  and  O  ;  C,  H,  N,  O,  and  S ;  C,  H, 
N,  O,  S,  and  P. 

Compounds  artificially  prepared  may  contain  Cl,  Br,  I,  As, 
Sb,  etc. 

QUALITATIVE  ANALYSIS. 

Presence  of  C  and  H  :  Shown  by  the  compound  charring 
when  heated  alone,  or  producing  CO2  and  H2O  when  heated 
with  cupric  oxide. 

Presence  of  nitrogen :  a.  Many  compounds  containing 
nitrogen,  when  burned,  evolve  an  odor  similar  to  that  of  burnt 
feathers. 


36  NOTES  ON  CHEMICAL  LECTURES. 

b.  Many    compounds    containing    nitrogen,    when     heated 
with  an  alkali  or  with  soda-lime,  give  rise  to  the  formation 
of  ammoniacal   gas  (NH3),  which   may  be  detected   by  its 
odor,  and,  when   in   solution,  by  its   forming  a  precipitate   of 
(NH4Cl)2PtCl4  on  the  addition  of  platinic  chloride. 

c.  To  detect  nitrogen  in  other  compounds,  they  are  heated 
with  a  small  piece  of  metallic  potassium  or  sodium,  thereby 
forming  cyanogen,  which  combines  with   the   potassium    or 
sodium  forming  a  cyanide,  the  residue  is  dissolved  in  water 
and  the  solution  tested  for  a  cyanide  with  FeSO4  -f  Fe2Cl6  + 
HC1,  =  formation  of  prussian  blue. 

Presence  of  sulphur :  a.  If  the  compound  be  a  solid,  it 
is  heated  with  a  mixture  of  solid  potassium  hydroxide  (KOH) 
(twelve  parts)  and  solid  potassium  nitrate  (KNO3)  (six  parts)  : 
the  sulphur  is  oxidized  to  sulphuric  acid  (which  combines 
with  the  potassium  to  form  K2SO4).  The  fused  mass  is  dis- 
solved in  water  and  tested  with  barium  chloride  for  a  sulphate. 

b.  If  the  compound  be  a  liquid,  it  is  boiled  with  nitric  acid 
alone  or  with  potassium  chlorate :  the  sulphur  is  oxidized  to 
sulphuric  acid.     The  liquid  is  tested  with  barium  chloride  for 
a  sulphate. 

If  the  compound  be  a  volatile  liquid,  it  is  heated  in  a 
sealed  glass  tube  with  about  twenty  to  thirty  times  its 
volume  of  nitric  acid  and  the  liquid  is  diluted  with  water  and 
tested  for  a  sulphate. 

c.  To  determine  if  the  sulphur  in  the  compound  is  directly 
(unoxidized)  or  indirectly  (oxidized)  combined  with  the  carbon, 
the  compound  is  heated  with  a  solution  of  potassium  hydrox- 
ide (KOH).     If  the  sulphur  is  directly  combined,  a  sulphide 
(K2S)  will  be  formed.     The  solution  is  tested  for  a  sulphide 
with  lead  acetate,  Pb(C2H3O2)2,  black  lead  sulphide  (PbS)  will 
be  formed,  or  tested  for  a  sulphide  with  sodium  nitroprusside 
(Na2NOFe(CN)5),  with  which  an  intense  purple-red  color  is 
produced.     If  the  sulphur  is  indirectly  combined,  the  solution 
will  not  respond  to  the  tests  for  a  sulphide,  but  in  some  cases 
may  respond  to  the  tests  for  a  sulphate. 

Presence  of  phosphorus :  a.  The  substance  is  fused  with 
the  mixture  before  stated  of  KOH  and  KNO3,  (a)  or  is  boiled 
with  nitric  acid,  as  in  the  case  of  sulphur,  and  the  aqueous 


^•*S  <r   tfay  a^ 

iMu^.._, 

a. 


a 


NOTES  ON  CHEMICAL  LECTURES.  37 

solution  tested  with  ammonium  chloride,  ammonium  hydrox- 
ide, and  magnesium  sulphate  (magnesia  mixture)  for  a  phos- 
phate (formation  of  a  crystalline  precipitate  of  MgNH4PO4). 

b.  If  the  organic  compound  be  a  volatile  liquid,  it  is  heated 
in  a  sealed  glass  tube  with  about  twenty  to  thirty  times  its 
volume  of  nitric  acid  and  the  liquid  is  diluted  with  water  and 
tested  for  a  phosphate. 

Presence  of  inorganic  matter ;  a.  The  substance  is 
heated  on  platinum  foil,  thereby  burning  off  the  organic 
matter,  and  leaving  the  inorganic  matter  as  a  fixed  residue. 

Presence  of  chlorine,  iodine,  or  bromine :  a.  The 
organic  compound  is  mixed  with  caustic  lime  (CaO),  and 
heated  in  a  combustion-tube.  The  mixture  is  suspended  in 
water,  slightly  acidulated  with  nitric  acid,  filtered,  and  the 
filtrate  tested  with  argentic  nitrate  for  a  chloride,  iodide  or 
bromide. 

QUANTITATIVE  ORGANIC  ANALYSIS. 

Ultimate  or  elementary  analysis  : 
Carbon          is  determined  as  CO2. 
Nitrogen       "  "  "  NH3  or  as  N. 

23'{  32 

Sulphur        "  "  "  SO3,   (BaSO4  =  S). 

222  62 

Phosphorus"  "  "  P2O5,    (Mg2P2O7  =  P2). 

Hydrogen     "  "  "  H2O. 

Oxygen  is  determined  by  difference, — /.  e.,  after  the  per- 
centages of  the  elements  in  the  compound  have  been  deter- 
mined the  percentages  are  added  together,  and  if  the  result 
does  not  foot  up  100,  the  difference  between  the  footing  and 
100  is  ascribed  to  oxygen. 

Conditions  to  be  observed  in  ultimate  analysis:  1. 
The  compound  to  be  analyzed  must  be  pure  and  dry.  A  crys- 
talline substance  maybe  purified  by  repeated  recrystallizations. 
The  compound  may  be  dried  by  allowing  it  to  remain  some 
time  over  sulphuric  acid  or  calcium  chloride  in  a  desiccator,  or 
it  may  be  dried  in  a  hot-water  or  air  oven.  When  two  weigh- 
ings agree  with  each  other, — /.  e.,  the  compound  ceases  to  lose 
weight, — it  is  considered  dry. 

2.  The  compound  must  be  completely  burned. 


38  NOTES  ON  CHEMICAL  LECTURES. 

3.  The  products  of  the  combustion  must  be  accurately  col- 
lected and  weighed  or  measured. 

Requisites  for  an  elementary  analysis  :  1.  A  combus- 
tion-tube of  difficultly  fusible  Bohemian  glass,  about  eighteen 
inches  in  length  and  drawn  out  at  one  end  in  a  bayonet-like 
form  and  sealed  at  the  drawn  out  end. 

2.  A  combustion-furnace. 

3.  An  aspirator. 

4.  A  gas-holder  containing  air  or  oxygen. 

5.  Cupric   oxide  (CuO)  or  fused  granular  lead   chromate 
(PbCrO4)  to  furnish  oxygen  during  the  progress  of  the  com- 
bustion. 

6.  A  U-shaped  tube  containing  calcium  chloride  to  absorb 
the  H2O  formed  in  the  combustion. 

7.  Geissler's  or  Liebig's  bulbs  containing  a  strong  solution 
of  potassium  hydroxide  to  absorb  the  CO2  formed  in  the  com- 
bustion. 

Method.  Determination  of  carbon  and  hydrogen :  A 
Bohemian  glass  combustion-tube  is  about  half  filled  with 
freshly  heated,  perfectly  dry,  granular  cupric  oxide  (or  lead 
chromate).  The  accurately  weighed  organic  compound  to  be 
analyzed  is  placed  in  the  tube  on  top  of  the  cupric  oxide,  some 
fine  cupric  oxide  added,  and  the  compound  thoroughly  mixed 
with  the  cupric  oxide  by  means  of  a  copper  wire  terminating 
in  a  spiral.  The  tube  is  then  filled  to  within  nearly  an  inch  of 
the  end  with  more  granular  cupric  oxide,  a  plug  of  loose 
asbestos  inserted,  the  tube  placed  on  a  combustion-furnace, 
and  a  previously  weighed  tube,  containing  calcium  chloride  in 
small  pieces  to  absorb  the  H2O  produced  in  the  combustion, 
is  attached  to  it  by  means  of  a  closely-fitting  perforated 
rubber  stopper.  Previously  weighed  Geissler's  or  Liebig's 
bulbs,  containing  a  solution  of  KOH  (specific  gravity  1.27)  to 
absorb  the  CO2  formed  in  the  combustion,  having  a  tube 
attached  containing  small  pieces  of  KOH  (previously  weighed 
with  the  Geissler's  bulbs)  to  absorb  the  last  traces  of  CO2,  and 
also  to  hold  any  moisture  that  might  be  carried  over  from  the 
KOH  solution  in  the  bulbs  by  the  current  of  gas,  are  attached 
to  the  calcium  chloride  tube. 

The  combustion-tube  is  heated  first  at  the  end  to  which  the 
calcium  chloride  tube  is  attached ;  when  the  cupric  oxide  in 


NO  TES  ON  CHEMICAL  LECTURES.  39 

this  part  of  the  tube  is  of  a  dull  red  heat  the  heating  is  com- 
menced at  the  other  end  of  the  tube,  and  continued  until  the 
cupric  oxide  in  that  part  is  also  of  a  dull  red  heat.  The  heat 
is  then  gradually  extended  to  the  middle  of  the  tube  until 
finally  the  whole  tube  is  heated.  The  heating  must  be  gradual, 
so  that  the  combustion  is  not  too  rapid,  or  some  of  the  products 
may  pass  through  the  absorption-bulbs  unabsorbed.  When 
the  combustion  is  completed  the  liquid  in  the  bulb  of  the 
Geissler's  bulbs  nearest  the  calcium  chloride  tube  will  ascend. 
An  aspirator  is  attached  to  the  Geissler's  bulbs,  and  a  rubber 
tube  leading  from  a  drying  apparatus  is  attached  to  the  bayonet- 
like  end  of  the  combustion-tube,  the  end  of  the  glass  tube 
broken  off  while  in  the  rubber  tube,  and  the  aspirator  started. 
Oxygen  or  air,  free  from  CO2  or  H2O,  is  slowly  drawn  from  the 
gas-holder  through  the  combustion-tube  to  burn  any  of  the 
organic  compound  which  may  have  escaped  decomposition, 
and  also  to  convey  any  CO2  or  vapor  of  H2O  remaining  in  the 
combustion-tube  into  the  Geissler's  bulbs  and  calcium  chloride 
tube.  The  drying  apparatus  through  which  the  oxygen  or  air 
is  caused  to  pass  before  entering  the  combustion-tube  is  com- 
posed of  a  series  of  three  cylinders,  the  first  containing  a  solu- 
tion of  KOH  to  absorb  CO2;  the  second  and  third  containing 
respectively  sulphuric  acid  and  pieces  of  calcium  chloride  to 
absorb  H2O.  After  drawing  oxygen  or  air  through  the  tube  a 
few  minutes  the  flames  are  extinguished,  the  Geissler's  bulbs 
and  the  calcium  chloride  tube  are  detached  (the  openings  stop- 
pered) and  allowed  to  cool.  When  cool  they  are  unstoppered 
and  weighed.  The  increase  in  weight  of  the  Geissler's  bulbs 
containing  the  KOH  will  indicate  the  quantity  by  weight  of 
CO2  which  resulted  from  the  combustion  of  the  carbon  in 
the  organic  substance  employed. 

The  increase  in  weight  of  the  tube  containing  calcium 
chloride  will  indicate  the  quantity  by  weight  of  H2O  which 
resulted  from  the  combustion  of  the  hydrogen  in  the  organic 
substance  employed. 

The  quantity  of  carbon  is  calculated  from  the  weight  of  CO2 
obtained,  as  follows : 

44         12 

CO2  :  C  ::  wt.  of  CO2  obtained  :  X 


40  NOTES  ON  CHEMICAL  LECTURES. 

The  quantity  of  hydrogen  is  calculated  from  the  weight  of 
H2O  obtained,  as  follows : 

18  2 

H2O  :  H2  ::  wt.  of  H2O  obtained  :  X 

If  the  compound  for  analysis  be  a  liquid,  it  is  placed  in  a 
small  weighed  glass  bulb  having  a  drawn-out  tube.  This  is 
accomplished  by  rarefying  the  air  in  the  bulb  by  heating  and 
holding  the  drawn-out  end  in  the  liquid.  On  cooling,  the 
liquid  will  ascend  and  occupy  the  space  of  the  expelled  air. 
The  tube  is  then  sealed  over  a  Bunsen  flame  and  the  bulb 
weighed.  The  increase  of  weight  is  the  weight  of  the  com- 
pound contained  in  the  bulb.  The  bulb  containing  the  liquid 
is  dropped  into  the  combustion-tube  containing  the  cupric 
oxide,  and  the  method  as  before  described  employed. 

If  the  compound  to  be  analyzed  contain  nitrogen  in  addi- 
tion to  the  carbon  and  hydrogen  or  oxygen,  oxides  of  nitrogen 
may  be  formed  during  the  combustion,  and  these  oxides  being 
absorbed  with  the  CO2  by  the  KOH  solution  in  the  Geissler's 
bulbs,  would  lead  to  inaccurate  results  by  apparently  increasing 
the  quantity  of  CO2.  In  this  case,  metallic  copper  (in  the 
form  of  turnings  or  gauze)  is  heated  in  a  current  of  hydrogen 
and  then  placed  in  the  combustion-tube,  at  the  end  at  which 
the  calcium  chloride  tube  is  attached,  in  order  to  decompose 
the  oxides  of  nitrogen  into  free  oxygen  and  nitrogen. 

If  sulphur  be  present  in  the  compound,  SO3  (sulphuric 
anhydride)  may  be  formed  in  the  combustion  and  be  absorbed 
with  the  CO2  by  the  KOH  in  the  Geissler's  bulbs.  In  this 
case,  PbO2  (lead  dioxide)  should  be  placed  in  the  combustion- 
tube  containing  the  cupric  oxide,  at  the  end  at  which  the 
calcium  chloride  tube  is  attached.  The  SO3  will  combine 
with,  and  be  held  by,  the  lead  as  PbSO4.  Lead  dioxide  need 
not  be  placed  in  the  tube  if  lead  chromate  instead  of  cupric 
oxide  is  used  in  the  combustion. 

Compounds  containing  chlorine,  iodine,  or  bromine  when 
burned  with  cupric  oxide  form  cupric  chloride,,  iodide,  or 
bromide,  which  volatilize  at  a  high  temperature  and  condense 
in  the  calcium  chloride  tube,  thus  causing  a  fictitious  increase 
in  the  weight  of  the  H2O.  Compounds  containing  these 


NOTES  ON  CHEMICAL  LECTURES.  41 

elements  must  be  burned  with  lead  chromate  (PbCrO4) ;  non- 
volatile plumbic  chloride,  iodide,  or  bromide  will  be  formed 
and  retained  in  the  combustion-tube. 

Compounds  difficult  of  combustion  should  be  burned  with 
lead  chromate  or  with  pure  oxygen.  The  latter  is  employed 
especially  for  coals  and  coke.  The  substance  to  be  burned 
is  placed  in  a  porcelain  boat,  and,  instead  of  glass,  an  iron 
combustion-tube  is  often  employed. 

DETERMINATION  OF  NITROGEN  METHODS : 

1.  Dumas'  method:  Depends  upon  the  decomposition  of 
the  organic  substance  with  the  evolution  of  all  of  the  nitrogen, 
which  is  collected  and  measured  in  a  eudiometer. 

The  nitrogenous  compound  is  burned  in  a  combustion-tube, 
sealed  at  one  end,  with  cupric  oxide  and  copper-wire  gauze  as 
in  the  determination  of  carbon  and  hydrogen,  except  that  a 
layer  of  about  three  inches  of  acid  sodium  carbonate  (NaHCO3) 
or  of  magnesite  (magnesium  carbonate,  MgCO3)  is  placed  at 
the  closed  end  of  the  tube.  When  filled  the  tube  contains 
the  following  substances  in  the  given  order: 

1.  NaHCO3  or  MgCO3  (to  the  depth  of  about  three  inches). 

2.  Cupric  oxide  (nearly  to  the  middle  of  the  tube). 

3.  Mixture  of  organic  substance  and  cupric  oxide. 

4.  Cupric  oxide. 

5.  Copper  gauze  to  decompose  oxides  of  nitrogen. 

A  delivery-tube  is  attached  to  the  open  end  of  the  combus- 
tion-tube (the  exit  of  the  delivery-tube  being  brought  below 
the  surface  of  mercury  contained  in  a  trough),  and  a  glass 
tube,  containing  mercury  and  a  solution  of  potassium  or 
sodium  hydroxide,  is  inverted  over  the  exit  of  the  delivery- 
tube.  The  acid  sodium  carbonate,  or  the  magnesium  carbonate 
is  heated  first.  Decomposition  takes  place  and  CO2  is  evolved. 

2NaHCO3  =  Na2CO3  -f  H2O  +  CO2 
MgC03  =  MgO  +  C02 

The  heating  of  the  carbonate  is  continued  until  all  the 
air  is  driven  out  of  the  combustion-tube  by  CO2.  This  is 


42  NO  TES  ON  CHE  MIC  A  L  L  E  C  7  URES. 

accomplished   when    the   bubbles  of  evolved   gas  are  com- 
pletely absorbed  by  the  KOH  solution. 

When  all  the  air  is  driven  out,  the  heating  of  the  carbonate 
is  discontinued,  and  the  KOH  tube  is  removed.  A  eudiometer, 
containing  mercury  and  a  layer  (about  three  or  four  inches  in 
thickness)  of  solution  of  KOH,  is  now  inverted  over  the  exit 
of  the  delivery-tube.  Heat  is  applied  to  the  end  of  the  tube 
(No.  5)  containing  the  copper  gauze,  and  also  to  the  part  con- 
taining cupric  oxide  (No.  2)  next  to  the  carbonate.  The  heat 
is  gradually  extended  to  the  middle  of  the  tube,  until  the  entire 
tube,  except  (No.  1)  carbonate  part,  is  heated.  The  heating 
is  discontinued  when  gas-bubbles  cease  to  come  over  into  the 
eudiometer.  At  this  time  the  acid  sodium  carbonate  is  again 
heated,  more  CO2  is  evolved  which  drives  out  the  remaining 
nitrogen.  The  heating  is  continued  until  the  gas-bubbles 
entering  the  eudiometer  are  completely  absorbed  by  the  KOH. 

The  CO2  and  H2O  produced  in  the  combustion  are  absorbed 
by  the  solution  of  KOH.  The  nitrogen  is  not  absorbed,  and 
collects  in  the  upper  part  of  the  eudiometer. 

The  eudiometer  containing  the  nitrogen  is  transferred  to  a 
vessel  of  water,  the  atmospheric  pressure  is  equalized,  and  the 
volume  of  nitrogen  read  off  and  corrected  for  temperature 
and  pressure. 

14  grm.  nitrogen  =  11160  c.c. 
11160  :  14  ::  1  c.c.  :  0.001256  grm. 
1  c.c.  of  nitrogen  at  0°  C.  and  760  mm.  weighs  0.001256  grm. 

2.  Will  and  Varrentrapp's  method  :  Depends  upon  the 
formation  of  NH3  (ammoniacal  gas)  when  an  organic  sub- 
stance containing  nitrogen  is  heated  with  soda-lime. 

This  method  is  not  applicable  for  the  determination  of  nitro- 
gen in  compounds  in  which  the  nitrogen  is  present  as  a  nitro 
group. 

A  combustion-tube  is  nearly  half-filled  with  dry  soda-lime. 
The  weighed  organic  substance  is  added  and  thoroughly 
mixed,  by  means  of  a  wire  stirrer,  with  the  soda-lime.  More 
soda-lime  is  added  until  the  tube  is  within  about  an  inch  of 
being  filled,  and  a  plug  of  loose  asbestos  is  placed  in  the  end. 


NOTES  ON  CHEMICAL  LECTURES.  43 

The  tube  now  contains  the  following  substances  in  the  fol- 
lowing order : 

1.  Soda-lime. 

2.  Mixture  of  organic  substance  and  soda-lime. 

3.  Soda-lime. 

4.  Plug  of  loose  asbestos. 

a.  Gravimetric  determination  of  nitrogen. 

The  combustion-tube  is  connected  with  Will's  bulbs,  con- 
taining dilute  hydrochloric  acid,  and  is  heated  in  a  combustion- 
furnace.  The  heating  should  be  commenced  simultaneously  at 
each  end  of  the  tube,  and  gradually  extended  to  the  middle. 

The  NH3  is  absorbed  by  the  HC1  in  the  Will's  bulbs,  forming 
NH4C1. 

The  contents  of  the  Will's  bulbs  are  emptied  into  a  dish ; 
excess  of  platinum  chloride,  which  precipitates  the  ammonia, 
is  added,  and  the  whole  evaporated  to  dryness  on  a  water-bath. 
The  residue  is  collected  on  a  weighed  filter  by  means  of  a 
mixture  of  alcohol  and  ether,  and  thoroughly  washed  with  a 
mixture  of  the  same  liquid. 

When  the  precipitate,  (NH4Cl)2PtCl4,  is  dry  it  is  weighed 
while  on  the  filter.  Every  100  parts  of  (NH4Cl)2PtCl4  con- 
tains 6.318  parts  of  nitrogen. 

(NH4CI)2PtC]4.       N2. 

443.3    :    28  ::   100  :  6.318 
or  the  quantity  of  nitrogen  may  be  calculated  as  follows : 

(NH4Cn2P'Cl4.       N2. 

443.3    :    28  :  weight  of  precipitate  :  X 

Instead  of  weighing  the  precipitate  as  (NH4Cl)2PtCl4,*it  may 
be  incinerated  and  weighed  as  metallic  platinum ;  then 

Every  100  parts  of  platinum  are  equivalent  to  14.410  parts 
of  nitrogen. 

Pt.          N2. 

194.3  :  28  ::  100  :  14.410 
or  the  quantity  of  nitrogen  may  be  calculated  as  follows : 

Pt.  N2. 

194.3  :  28  ::  weight  of  metallic  platinum  :  X 

6 


44  NOTES  ON  CHEMICAL  LECTURES. 

b.  Volumetric  determination  of  nitrogen. 

A  measured  volume  of  a  normal  solution  of  oxalic  acid 
(H2C2O4  +  2H2O)  may  be  used  in  the  Will's  bulbs,  instead  of 
dilute  HC1,  to  absorb  the  NH3,  and  the  quantity  of  nitrogen 
calculated  from  the  number  of  cubic  centimetres  of  oxalic 
acid  solution,  neutralized  by  the  NH3,  as  determined  by  titer- 
ing  with  a  normal  solution  of  NaOH. 

H2C2O4  -f  2H.,O,  a  dibasic  acid. 

126  -63 
~2~ 

H2C2O4  +  2H2O  +  2NH3  =  (NH4)2C2O4  +  2H2O 

Oxalic  acid.  NH3. 

126  grm.  =  34  grm. 
63     "     =-17     " 

A  normal  solution  of  oxalic  acid  is  prepared  by  dissolving 
63  grm.  of  pure  oxalic  acid  in  1000  c.c.  water ;  then 

Oxalic  acid.  NH3.  N. 

1000  c.c.  =  63.0    grm.  ==  17.0    grm.  ==  14.0    grm. 
1  c.c.  =    0.063  "     =    0.017  "      =    0.014  " 

10  c.c.  of  the  oxalic  acid  solution  are  placed  in  the  Will's 
bulbs.  The  combustion  of  the  organic  compound  is  performed 
and  the  NH3  evolved  is  absorbed  by  the  oxalic  acid  solution, 

When  the  combustion  is  completed  the  oxalic  acid  solution 
in  the  Will's  bulbs  is  emptied  into  a  beaker,  the  bulbs  rinsed 
with  water  and  the  wash  water  also  placed  in  the  beaker,  a 
few  drops  of  litmus  added,  and  the  oxalic  acid  solution  titered 
with  a  normal  solution  of  NaOH. 

1000  c.c.  of  normal  sol.  of  NaOH  contains  40.0  grm.  NaOH. 
1  c.c.  "        "  "  "  "          0.040  " 

0.040  NaOH  =  0.063  oxalic  acid. 

Consequently  1  c.c.  normal  solution  of  NaOH  is  equal  to 
(will  neutralize)  1  c.c.  normal  oxalic  acid  solution,  and  10  c.c. 
normal  NaOH  solution  are  equal  to  10  c.c.  normal  oxalic  acid 
solution. 

On  titering  the  10  c.c.  oxalic  acid  solution  from  the  Will's 
bulbs,  it  will  now  be  found  that  less  than  10  c.c.  of  normal 


* 


NOTES  ON  CHEMICAL  LECTURES.  45 

NaOH  solution  will  be  required,  showing  that  some  of  the 
oxalic  acid  has  been  neutralized  by  the  NH3. 

Suppose  only  6  c.c.  of  normal  NaOH  solution  were  required 
to  neutralize  the  10  c.c.  oxalic  acid  solution  from  the  Will's 
bulbs,  then  the  difference  between  6  and  10  =  4  indicates  the 
number  of  cubic  centimetres  of  oxalic  acid  solution  neutralized 
by  the  NH3  which  resulted  from  the  combustion  of  the  organic 
compound. 

1  c.c.  of  oxalic  acid  solution  is  neutralized  by  0.017  NH3, 
equivalent  to  0.014  N,  and  as  4  c.c.  were  neutralized  then 
4  X  0.014  =  0.056  grm.  nitrogen  present  in  the  weight  of 
organic  compound  analyzed. 

3.  Kjeldahl's  method:  Depends  upon  the  conversion  of 
the  nitrogen  in  a  compound  into  ammonia,  by  boiling  it  with 
sulphuric  acid.  The  ammonia  combines  with  the  sulphuric 
acid  to  form  ammonium  sulphate.  The  ammonium  sulphate, 
(NH4)2SO4,  is  decomposed  into  NH3  and  Na2SO4  by  boiling  it 
with  sodium  hydroxide.  The  evolved  ammoniacal  gas  (NH3) 
is  collected  in  dilute  hydrochloric  acid  and  precipitated  with 
platinum  chloride  as  (NH4Cl)2PtCl4. 

The  precipitate  is  collected  on  a  filter,  washed  with  a  mix- 
ture of  alcohol  and  ether,  and  treated  exactly  as  in  Will  and 
Varrentrapp's  method. 

The  NH3  may  also  be  collected  in  a  measured  volume  of 
normal  oxalic  acid  solution  and  titered  with  a  normal  solution 
of  sodium  hydroxide,  as  in  Will  and  Varrentrapp's  method. 

DETERMINATION  OF  SULPHUR. 

Sulphur  in  an  organic  compound  is  determined  quantita- 
tively by  fusing  the  compound  with  about  12  parts  of  potas- 
sium hydroxide  (KOH)  and  6  parts  of  potassium  nitrate 
(KNO3),  or  by  boiling  the  compound  with  nitric  acid,  as  in 
the  qualitative  detection  of  sulphur.  The  sulphur  is  oxidized 
to  sulphuric  acid,  the  latter  is  then  precipitated  with  barium 
chloride  (BaCl2)  as  barium  sulphate  (BaSO4),  and  the  quantity 
of  sulphur  is  calculated  from  the  amount  of  BaSO4  obtained. 
233  parts  of  BaSO4  (molec.  wt.)  =  32  parts  of  S. 

BaSO4.  S. 

233    :    32  : :  wt.  of  precipitate  (BaSO4)  :  x 


46  NOTES  ON  CHEMICAL  LECTURES. 

DETERMINATION  OF  PHOSPHORUS. 

Phosphorus  is  determined  quantitatively  by  fusing  the 
compound  with  1 2  parts  of  KOH  and  6  parts  of  KNO3,  or  by 
boiling  it  with  HNO3,  as  in  the  determination  of  sulphur. 
The  phosphorus  is  oxidized  to  phosphoric  acid,  which  is 
precipitated  by  the  magnesia  mixture  (NH4C1  -j-  NH4HO  -f- 
MgSO4),  and  weighed  as  magnesium  pyrophosphate,  Mg2P2O7. 

222  parts  of  Mg2P2O7  (molec.  wt.)  =  62  parts  of  P. 

Mg»P207.        P. 

222    :    62  ::  wt.  of  magnesium  pyrophosphate  :  x 

DETERMINATION  OF  CHLORINE,  BROMINE,  AND  IODINE. 

Chlorine,  bromine,  and  iodine  are  determined  quantita- 
tively by  heating  the  compound  in  which  the  element  is  con- 
tained, in  a  combustion-tube  with  caustic  lime,  as  in  the 
qualitative  detection  of  these  elements,  dissolving  in  water, 
filtering,  neutralizing  with  HNO3  and  precipitating  with  argentic 
nitrate  (AgNO3),  and  weighing  as  argentic  chloride  (AgCl), 
argentic  bromide  (AgBr),  and  argentic  iodide  (Agl). 


CALCULATION  OF  RESULTS  AND  DEDUCTION  OF 
FORMULAS. 

Rule  :  Determine  the  percentages  of  all  the  elements  in  the 
compound.  Divide  the  percentage  of  each  element  by  its 
atomic  weight.  Then  divide  the  quotients  obtained  by  the 
smallest  quotient,  and,  if  necessary,  multiply  these  final 
quotients  by  the  least  number  that  will  make  all  of  them 
whole  or  nearly  whole  numbers.  The  formula  thus  obtained 
is  the  empirical  formula,  and  at  the  same  time  may  be  the 
molecular  formula.  The  molecular  formula  is  determined  by 
observing  the  vapor  density  of  the  compound,  etc. 

Example  :  A  combustion  of  0.340  grm.  of  oil  of  turpen- 
tine, a  compound  containing  only  carbon  and  hydrogen, 
furnished 

CO2 1.100  grm. 

H2O .  0.360     " 


NOTES  ON  CHEMICAL  LECTURES.  47 

CO,.        C.       Wt.  ofCO2.        C. 

then,       a.  44  :  12  ::  1.100  :  0.300  grm. 

HoO.    H.,.      Wt.ofH2O.         H. 

18  :  2  ::  0.360  :  0.040  grm. 
Hence  0.340  grm.  of  the  oil  contained 

0.300  carbon. 
0.040  hydrogen. 

Oil.  C. 

b.  0340  :  0.300  ::  100  :  88.235  per  cent,  carbon. 

Oil.  H. 

0.340  :  0.040  ::  100  :  11.765  per  cent,  hydrogen. 
The  percentage  composition  is, — 

Carbon 88.235 

Hydrogen 11  765 

100.000 

c.  88.235  H-  12  =  7.353  -*-  7.353  =1x5  =  5  atoms  C. 
11.765  -H  1  =  11.765  -H  7.353  =  1.599  X  5  =  7.995  atoms  H, 
or,  approximately,  8  atoms  of  H. 

Hence  the  empirical  formula  of  oil  of  turpentine  is  C5HS. 
(The  molecular  formula  is  twice  C3H8,  or  C10H16.) 
Or,  if  0.340  grm.  oil  of  turpentine  furnished 

CO2 *.  .  .  1.100  grm. 

H2O 0.360  " 

Oil.     CO2.  COo. 

then,      a.  0.340  :  1.100  ::  100  :  323.53  grm. 

Oil.  Hj-O.  H2O. 

0.340  :  0.360  ::  100  :  105.88  grm. 

If  100  grm.  of  the  oil  yields  323.53  grm.  CO2  and  105.88 
grm.  H2O,  then  to  obtain  the  percentage  proportions  of  carbon 
and  hydrogen, — 

co.,.     c. 
b.  44  :  12  ::  323.53  :  88.235  per  cent,  carbon. 

H2O.      H2. 

18  :     2  ::  105.88  :  11.765  percent,  hydrogen. 


48  NOTES  ON  CHEMICAL  LECTURES. 

And  from  these  percentages  of  carbon  and  hydrogen  we  find, — 

^.88.235-^-12=   7.353 -f- 7,353  =  1         X  5  =  5  atoms  C. 
11.765--   1  =  11. 765  -T- 7.353  =  1.599  X  5  =  7.995  atoms  H, 

or,  approximately,  8  atoms  of  H. 

Hence  the  empirical  formula  for  the  compound  is  C5HS. 

Oxalic  acid  is  composed  of, — 

Carbon 26.66  per  cent. 

Hydrogen 2.22 

Oxygen 71.12 

100.00 
Then, 

C  26.66  ~l'2  =  2.22  -*-  2.22  =  1  atom  carbon. 
H    2.22 -f-    1  =  2.22  ~-  2.22  =  1     "       hydrogen. 
O  71.12  -4-  16  =  4.44  -4-  2  22  =  2  atoms  oxygen. 

Hence  the  empirical  formula  of  oxalic  acid  is  HCO2.  (The 
molecular  formula  is  twice  HCO2,  or  H2C2O4.) 

Composition  of  cane  sugar  according  to  Liebig, — 

Carbon 42.30  =  1.001 

Hydrogen    .......      6.45  =  2.009 

Oxygen 51.25  =  1  OOP 

100.00 

Formula  for  cane  sugar  according  to  different  chemists, — 

Berzelius    . C^H^On 

Doebereiner C6H12O6 

Dumas C5H10O5 

Prout C8H16O8 

THE  URINE. 

The  urine  is  the  secretion  of  the  kidneys,  in  which  effete 
nitrogenized  products  are  thrown  out  from  the  system. 

The  color  of  normal  urine  is  yellow.  The  intensity  of  color 
is  proportionate  to  the  specific  gravity,  except  diabetic  urine, 
in  which  the  specific  gravity  may  be  high  and  the  color  pale 
yellow. 


NOTES  ON  CHEMICAL  LECTURES.  49 

The  reaction  of  normal  urine  just  voided  is  usually  acid. 
The  acid  reaction  is  not  due  to  the  presence  of  free  acid  but  to 
acid  salts,  principally  to  acid  sodium  phospJiate  (NaH2PO4) 
arising  from  the  sodium  phosphate  (Na2HPO4)  of  the  blood 
coming  in  contact  with  the  uric  acid  of  the  urine. 

2Na2HPO4  +  H2C5H2N4O3  =  2NaH2PO4  +  Na2C5H2N4O3 

Neutral  sodium  phosphate.        Uric  acid.          Acid  sodium  phosphate.     Neutral   sodium  urate. 

Urine  having  an  alkaline  reaction  may  be  voided,  especially 
after  a  very  hearty  meal,  and  also  after  the  ingestion  of  alkalies 
and  substances,  as  the  acetates,  tartrates,  and  citrates  (lemon- 
juice)  of  the  alkalies,  which  in  the  organism  are  converted 
into  and  voided  as  alkaline  carbonates. 

On  the  ingestion  of  acids,  urine  having  a  strong  acid  reac- 
tion may  be  voided. 

Normal  urine,  on  standing  some  time,  may  become  alkaline 
in  reaction,  due  to  the  presence  of  ammonium  carbonate 
resulting  from  the  action  of  certain  micro-organisms  (micro- 
coccus  ureae)  on  the  urea. 

CO(NH2)2  +  2H20  =  (NH4)2C03 

Urea.  Ammon.  carbonate. 

Normal  urine  may  have  an  amphoteric  reaction, — /.  e., 
changing  blue  litmus-paper  to  red,  and  red  litmus  to  blue, — 
due  to  the  simultaneous  presence  in  the  urine  of  acid  and 
neutral  phosphates. 

In  collecting  urine  for  a  quantitative  determination  of  its 
constituents,  the  total  quantity  voided  in  24  hours  should  be 
collected  and,  that  the  liquid  collected  shall  be  homogeneous 
in  constitution,  the  separate  portions  collected  during  the  24 
hours  must  finally  be  placed  in  one  bottle  and  thoroughly 
mixed. 

In  collecting  the  urine  passed  in  24  hours  the  collection 
should  be  begun  at  a  certain  time.  For  example,  at  8  a.  m.  of 
one  day  the  bladder  should  be  emptied  and  this  portion  of 
urine  discarded.  The  urine  voided  from  this  time  until  8 
a.  m.  the  next  day  (at  which  time  the  bladder  should  be  finally 
emptied),  should  be  collected  in  a  bottle, — including  that  voided 
in  the  final  emptying  of  the  bladder.  During  the  period  of 
collection  the  urine,  voided  should  be  kept  in  a  cold  place. 


50  NOTES  ON  CHEMICAL  LECTURES. 

Acidity  of  the  urine  :  The  acidity  of  the  average  quantity 
of  urine  voided  in  a  day  will  require  from  1.0  to  1.5  grm. 
NaOH  to  neutralize  it. 

The  average  quantity  of  sodium  acid  phosphate  (NaH2PO4) 
daily  eliminated  in  the  urine  is  equivalent  to  about  2.3  grm. 
of  phosphoric  anhydride  (P2O5),  and  to  convert  2.3  grm.  P2O5 
as  NaH2PO4  into  Na2HPO4  will  require  1.3  grm.  NaOH. 

The  acidity  of  the  urine  is  determined  by  means  of  a  deci- 
normal  solution  of  sodium  hydroxide  (NaOH). 

A  normal  solution  of  NaOH  contains  40.0  grm.  of  NaOH 
in  1000  c.c.  distilled  water.  A  deci-normal  solution  contains 
TV  of  40.0,  or  4.0  grm.  of  NaOH  in  1000  c.c.  of  distilled 
water. 

NaOH. 

1000  c.c.  ==  4.0      grm. 
1  c.c.  =  0.004    " 

Method  :  To  100  c.c.  of  urine,  two  or  three  drops  of  rosolic 
acid,  or  of  phenol-phthalein  solution  are  added,  a  deci-normal 
solution  of  NaOH  is  run  in  from  a  burette  until  a  change 
takes  place  in  the  color  of  the  indicator  (rosolic  acid,  or  phenol- 
phthalein),  the  number  of  c.c.  NaOH  solution  required  to 
produce  the  change  in  color  is  read  off,  and  this  number  is 
multiplied  by  the  value  of  1  c.c.  of  the  deci-normal  solution 
expressed  in  NaOH  units, — namely,  0.004. 

Example  :  24  hours  urine  =  1200  c.c. 

100  c.c.  of  the  urine  required  30.  c.c.  NaOH  solution. 

30  X  0.004  =  0.120  grm.  NaOH  required  for  100  c.c.  urine. 

12  X  0.120  =  1.440  grm.   NaOH  required  to  neutralize  the 

acidity  of  1200  c.c.    urine  (quantity  of  urine  voided  in   24 

hours). 

Specific  gravity  of  urine  :  The  specific  gravity  of  normal 
urine  varies  from  1015  to  1025.    The  average  is  about  4017, 
water  taken  as  1000. 

The  specific  gravity  may  be  as  low  as  1003  or  even  lower, 
and  as  high  as  1030  or  higher. 

The  specific  gravity  may  be  determined  by — 

a.  Urinometer. 

b.  Specific  gravity  bottle  (picnometer). 


NOTES  ON  CHEMICAL  LECTURES.  51 

The  specific  gravity  is  affected  by  temperature.  It  should 
be  taken  with  the  liquid  at  a  temperature  of  15°  C.  or 
60°  F. 

The  specific  gravity  is  lowered  one  unit  (the  specific  gravity 
of  water  expressed  as  1000)  for  every  increase  of  3°  C.  tem- 
perature. 

Determination  of  quantity  of  solid  matter  in  urine  ; 
1.  A  ready  method  is  to  evaporate  10  c.c.  urine,  in  a  weighed 
dish,  to  dryness  on  a  water-bath.  The  residue  is  further  dried 
in  a  drying-oven  at  100°  C.,and  placed  in  a  dessicator.  After 
a  time  it  is  weighed,  and  the  drying  operation  and  weighing 
are  repeated  until  a  constant  weight  is  obtained.  The  final 
weight,  minus  the  weight  of  the  dish,  is  the  amount  of  solid 
matter  in  10  c.c.  of  the  urine. 

This  method  is  not  very  accurate,  because  during  the  evapo- 
ration some  of  the  urea  is  decomposed  with  the  evolution  of 
ammoniacal  gas  (NH3),  thus  — 


a.  CO(Nfi     -f  H2O  =  2NH3  +  CO2 

b.  NH3  4  CO2  +  H2O  =  NH4HCO3 

c.  NaH2PO4  +  NH3"=  NaNH4HPO4 

d.  NaNH4HPO4  at  100°  C.  =  NaH2PO4  +  NH3 

2.  An  accurate  method  is  to  evaporate  to  dryness  2  c.c. 
urine  in  a  weighed  porcelain  boat  in  Neubauer's  special  drying 
apparatus,  collecting  the  NH3  which  results  from  the  decom- 
position  of  some  of  the  urea  and  finally  weighing  the  boat 
with  the  dry  residue.  The  NH3  evolved  from  the  decom- 
position of  the  urea  in  the  process  of  drying  is  collected  in  a 
normal  solution  of  sulphuric  acid  and  the  quantity  of  the  latter 
neutralized  by  the  NH3  is  determined  by  means  of  a  normal 
NaOH  solution,  and  from  the  quantity  neutralized  the  equiv- 
alent of  urea  is  deduced  and  the  weight  of  urea  found  to  hr\v 
been  decomposed  in  the  operation  of  drying  is  added  to  the 
weight  of  the  dry  residue  in  the  porcelain  boat. 

2  molecules  ammonia.         1  molecule  urea. 

2NH3    —     CO(NH2)2 
Or, 

34  parts  of  ammonia  =  60  parts  of  urea. 


52  NOTES  ON  CHEMICAL  LECTURES. 

Example  :  2  c.c.  urine  employed. 

Weight  of  boat  plus  residue  ....  0.640  grm. 

minus    "      ...    .  0.600     " 
Weight  of  dry  residue  ....  0.040     " 

The  NH3  evolved  was  collected  in  10  c.c.  normal  solution 
of  sulphuric  acid.  After  collecting  the  NH3  in  the  10  c.c. 
of  normal  solution  of  sulphuric  acid,  the  latter  was  titered 
with  a  normal  solution  of  sodium  hydroxide.  8  c.c.  of  the 
NaOH  solution  were  required  to  neutralize  the  10  c.c.  of 
sulphuric  acid  solution.  Previous  to  the  collection  of  the 
NH3  in  the  10  c.c.  normal  solution  of  sulphuric  acid,  10  c.c. 
of  normal  solution  of  sodium  hydroxide  would  have  been 
required  to  neutralize  it.  Now,  however,  some  of  the  sulphuric 
acid  has  been  neutralized  by  the  NH3  and  consequently  a  less 
volume  of  sodium  hydroxide  solution  will  be  required  to 
neutralize  the  10  c.c.  of  normal  sulphuric  acid  solution.  As 
8  c.c.  of  normal  sodium  hydroxide  solution  were  required  it 
indicates  that  2  c.c.  of  the  normal  sulphuric  acid  solution  were 
neutralized  by  the  ammonia  evolved. 

Thus, 

1  c.c.  of  normal  sulphuric  acid  solution  =  0.017  grm.  NH3 

2  c.c.  =  2  X  0.017  =  0.034  grm.  NH3 

As  34  parts  of  NH3  equal  60  parts  of  urea,  therefore, 

NH3.     Urea  NHS. 

34  :  60  ::  0.034  :  x  =  0.060  grm.  urea. 

Weight  of  residue  in  porcelain  boat 0.040  grm. 

Weight  of  urea  as  determined  by  amount  of  NH3 

evolved 0.060     " 

Weight  of  solid  matter  in  2  c.c.  of  the  urine  .  0.100     " 

c.c.         grm.  c.c. 

2  :  0.100  ::  100  :  x  =  5.0  grm.  solid  matter. 

3.  The  solid  matter  may  be  approximately  determined  by 
multiplying  the  last  two  figures  of  the  specific  gravity  by 
Haeser  and  Neubauer's  factor,  2.33.  Thus  if  the  specific 
gravity  is  1017, 

17  X  2.33  =  39.61  grm.  solid  matter  in  1000  c.c.  of  the  urine. 


iV\ 


NOTES  ON  CHEMICAL  LECTURES. 


53 


Or  more  closely,  (if  the  specific  gravity  be  expressed  with  five 
figures),  by  multiplying  the  last  three  figures  by  the  factor 
0.233.  Thus  if  the  specific  gravity  is  1020.3, 

203  X  0.233  =  47.299  grm.  solid  matter  in  1000  c.c.  of  the  urine. 


AVERAGE  COMPOSITION  OF  HUMAN  URINE. 


Water      

950.00 
28.00  ^ 
0.60  j 
0.35 
0.651 
8.00  ) 
8.00 
2.00 
1.25 
0.25 
0.30 

O.GOy 

Voided  per  day. 
Grains.          Grammes. 

,                    520.80        35.00 

(Organic                      11   16                  075 
'   matter.                                                      v>  '  J 

37.60               6.51           0.44 
|                      12.09          0.81 
148.80         10.00 
148.80         10.00 
37.20          2.50 

'maTtef                  23.45                 1.56 

12.40              4.65           0.31 
5.58          0.37 

11.16          0.75 

Urea    .    

Uric  acid     

Hippuric  acid  

Creatinine   

Kxtractives  

Sodium  chloride     .    .    . 
Phosphoric  acid  .... 
Sulphuric  acid    .... 
Lime  (CaO)    .    .        .    . 

Magnesia  (MgO)   .    .    . 
Potash  (K2O)  and  soda 
(Na2O)     

Water  

1000.00                      930.20 

950.00 
37.60                      699.36 
12.40                       230,34 

62.49 

47.00 
15.49 

Organic  matter  .... 
Inorganic  matter    .    .    . 

Average  quantity  of  urine  voided  per  day,  about  40  fluid- 
ounces,  or  1200  c.c.  • 


ANALYSIS  OF  THE  URINE. 

The  analysis  of  urine  may  have  for  its  object — 

1.  The  qualitative  detection  of  the  normal  and  abnormal 
constituents. 

2.  The  quantitative  determination  of  the  normal  and  ab- 
normal constituents. 

The  percentages  ot  solids  in  urine  are  expressed  as  per- 
centages by  volume, — /.  e.,  100  c.c.  by  volume  contain  a  given 
weight  of  a  solid. 


54  NOTES  ON  CHEMICAL^LECTURES. 

DETERMINATION  OF  SODIUM  CHLORIDE  (NaCI)  IN 

URINE. 

The  chlorine  in  urine  is  in  combination  as  a  chloride,  chiefly 
as  sodium  chloride  (NaCI). 

It  may  be  detected  qualitatively  by  strongly  acidulating  the 
urine  with  nitric  acid  and  adding  a  solution  of  argentic  nitrate 
(AgNO3).  If  NaCI  be  present  in  rather  large  quantity,  a  curdy 
precipitate  of  argentic  chloride  (AgCl)  will  be  formed ;  if  the 
quantity  present  be  small,  only  a  milkiness  will  be  produced. 
If  the  urine  contain  albumen,  it  must  be  removed  before 
making  this  test. 

QUANTITATIVE,, DETERMINATION  OF  SODIUM  CHLORIDE. 

1.  Gravimetric  method ;  Principle :  when  argentic  nitrate 
(AgNO3)  is  added  to  sodium  chloride  (NaCI)  all  of  the  chlorine 
is  precipitated  as  argentic  chloride  (AgCl). 

143.5. 

AgNO3  +  NaCI  =  AgCl  -j-  NaNO3 

The  quantity  of  sodium  chloride,  or  of  chlorine,  is  calculated 
from  the  quantity  of  AgCl  obtained. 

Every  143.5  parts  of  AgCl  =  58.5  NaCI  or  35.5  Cl. 
Hence 

AgCl.          NaCI.  NaCI. 

143.5  :  58.5  ::  weight  of  precipitate  of  AgCl  :  X 
or, 

AgCl.  Cl.  Cl. 

143.5  I  35.5  ::  weight  of  precipitate  of  AgCl  :  X 

Method :  10  c.c.  of  urine,  to  which  is  added  about  2  grm. 
potassium  nitrate  (KNO3)  to  destroy  the  organic  matter,  are 
evaporated  to  dryness  in  a  small  porcelain  evaporating  dish  on 
a  water-bath  (absolute  dryness  cannot  be  obtained)  or  over  a 
flame,  care  being  taken  to  'avoid  loss  from  spurting.  (The 
contents  of  the  dish  must  not  be  stirred.)  The  dish  con- 
taining the  residue  is  held  by  means  of  a  crucible  tongs  over 
a  flame  and  heated,  very  gently  at  first,  then  with  strong  heat, 
until  all  the  organic  matter  is  destroyed  as  indicated  by  the 
disappearance  of  the  charred  material.  The  dish  containing  the 
residue  while  cooling  is  held  at  the  outer  edge  by  a  crucible 


NOTES  ON  CHEMICAL  LECTURES.  55 

tongs  and  given  a  rotary  motion  until  the  fused  material  has 
distributed  itself  as  a  thin  layer  over  the  dish  and  finally 
solidified.  By  this  procedure  the  cracking  of  the  dish  will  be 
prevented.  Care  must  be  taken  that  in  this  procedure  none  ot 
the  fused  material  comes  in  contact  with  the  crucible  tongs  or 
is  projected  from  the  dish.  When  the  dish  is  thoroughly 
cooled  the  residue  is  treated  with  5  c.c.  of  water  and  eight  or 
ten  drops  of  strong  nitric  acid.  The  nitric  acid  is  added  to 
neutralize  the  KOH  and  K2CO3,  which  are  produced  in  the 
decomposition  of  the  KNO3,  with  the  organic  matter.  The 
liquid  in  the  dish  is  warmed  to  hasten  solution.  This  first  por- 
tion of  5  c.c.  is  poured  into  a  beaker  (keeping  back  any  enamel 
that  may  have  separated  from  the  dish),  and  washing  the  dish 
with  portions  of  5  c.c.  of  water  is  repeated  (without  further 
addition  of  nitric  acid),  and  heating,  if  necessary,  until  the  dish 
has  been  thoroughly  washed.  Each  portion  of  5  c.c.  is  poured 
into  the  beaker  until  30  c.c.  have  been  employed  and  collected 
in  the  beaker.  If  the  liquid  is  not  acid  in  reaction,  it  must  be 
acidulated  with  nitric  acid.  The  solution  is  warmed  and  excess 
of  AgNO3  solution  is  added.  The  liquid  is  stirred  with  a  glass 
rod  until  the  precipitate  separates  in  curd-like  masses.  The 
precipitate  is  collected  on  a  filter,  and  washed  with  distilled 
water  until  the  filtrate  shows  no  trace  of  the  presence  of  silver. 
This  is  determined  by  collecting  in  a  test  tube  a  portion  of  the 
filtrate  as  it  comes  from  the  funnel  and  adding  hydrochloric 
acid.  The  precipitate  is  dried  while  still  on  the  filter,  as  much 
as  is  possible,  is  detached  from  the  filter,  and  placed  in  a 
weighed  crucible.  The  folded  filter  is  held  by  means  of  a 
platinum  wire  over  the  crucible,  ignited,  and  the  ash  allowed 
to  fall  into  the  crucible.  The  ash  is  moistened  with  two  or 
three  drops  of  strong  nitric  acid  to  dissolve  the  metallic  silver 
which  may  have  resulted  from  the  reduction  of  AgCl  in  burn- 
ing the  filter,  and  the  crucible  is  warmed  very  gently.  When 
cool,  the  ash  is  moistened  with  two  or  three  drops  of  hydro- 
chloric acid  to  reprecipitate,  as  chloride,  the  silver  dissolved 
by  the  nitric  acid.  The  excess  of  acid  is  expelled  by  gently 
heating  the  crucible  over  a  very  small  flame.  The  crucible  is 
allowed  to  cool  and  is  then  weighed.  The  weight  of  the 
empty  crucible  and  the  filter  ash  is  deducted  from  the  weight 


56  NOTES  ON  CHEMICAL   LECTURES. 

of  the  crucible,  precipitate  and  ash.     The  difference  in  weights 
is  the  weight  of  the  argentic  chloride. 
Example  : 

Weight  of  crucible  +  prec.  +  filter  ash  ...  10.623 
"       "        "         —     "     —     "       "...  10.420 

"       "  prec.  -f-  filter  ash 0.203 

"       "  filter  ash 0.003 

"       "  prec.  of  AgCl 0.200 

Calculation : 

AgCl.         NaCl. 

143.5  :  58.5  ::  weight  of  precipitate  of  AgCl  :  X  =  quantity 
of  sodium  chloride  in  the  volume  (10  c.c.)  of  urine  employed. 
Multiply  by  10  =  percentage  of  NaCl. 

Or, 

AgCl.  Cl. 

143.5  :  35.5  ::  weight  of  precipitate  of  AgCl  :  X  =  quantity  of 
chlorine  in  the  10  c.c.  urine  employed.  Multiply  by  10  =  per- 
centage of  chlorine. 

If  0.200  grm.  AgCl  obtained,  then 

AgCl.          NaCl.       Wt.  of  prec.         NaCl.  NaCl. 

143.5  :  58.5  ::  0.200  :  0.08153  X  10  =  0.8153  per  cent,  in  a 

volume  of  100  c.c.  urine. 
In  100  grm.  of  urine. 

Suppose  specific  gravity  of  urine  was  1020. 

NaCl. 

Then,  1020  :  1000  ::  0.815  :  0.799  per  cent,  in  100  grm.  of 
the  urine. 

2.  Mohr's  volumetric  method  for  the  determination  of 
sodium  chloride ;  Depends  upon  the  precipitation  of  the 
chlorine  of  the  sodium  chloride  by  means  of  a  standard  solu- 
tion of  argentic  nitrate  and  calculating  the  quantity  of  sodium 
chloride  present  from  the  quantity  of  standard  solution 
required  for  complete  precipitation. 

The  standard  solution  of  argentic  nitrate  is  prepared  of 
convenient  strength, — /.  e.,  so  that  1  c.c.  of  the  solution  shall 
equal  0.010  of  NaCl.  1  c.c.  of  the  solution  is  also  equal  to 
0.006068  chlorine,—/,  e., 

NaCl.         Cl.  NaCl.  Cl. 

58.5  :  35.5  ::  0.010  :  0.006068 


NOTES  ON  CHEMICAL  LECTURES.  57 

Preparation  of  the  standard  solution  of  AgNO3 : 

58.5.  170. 

NaCl  +  AgNO3  =  AgCl  +  NaNO3 

58.5.      At.  wt.of  Ag,  108. 

NaCl  +  AgNO3  =  AgCl  +  NaNO3 

170  grm.  of  AgNO3  are  equal  to  58.5  grm.  of  NaCl. 

170  grm.  of  AgNO3  (equal  to  58.5  grm.  NaCl)  contain  108 
grm.  of  metallic  silver,  consequently  108  grm.  of  silver  are 
also  equal  to  58.5  grm.  of  NaCl. 

The  quantity  of  AgNO3  necessary  to  prepare  1000  c.c.  of 
standard  solution  so  that  1  c.c.  of  it  shall  equal  0.010  NaCl 
or  0.006068  Cl  is  determined  by 

NaCl.          AgNO3.       Grm.  NaCl.          AgNO3. 

58.5    :    170    ::     10     :     29.059  grm. 

Or  of  metallic  silver  to.  be  converted  into  nitrate,  by  treating 
with  nitric  acid,  evaporating  excess  of  acid,  and  dissolving  the 
residue  in  water,  and  diluting  to  1000  c.c. 

NaCl.  Ag.          Grm.  NaCl.        Metallic  silver. 

58.5     :      108      ::      10     :      18.461  grm. 

Preparation  of  standard  solution  of  argentic  nitrate : 
29.059  grammes  pure,  dry  AgNO3  are  dissolved  in  distilled 
water  and  the  solution  diluted  with  distilled  water  to  a  volume 
of  1000  c.c. 

Or,  18.461  grammes  pure  metallic  silver  are  dissolved  in 
nitric  acid,  the  excess  of  acid  is  expelled  by  evaporation  on  a 
water-bath  and  the  residue  (which  is  AgNO3)  is  dissolved  in 
distilled  water,  and  the  solution  diluted  with  water  to  1000  c.c. 
Then, 

AgNO3.  NaCl. 

1000  c.c.  =  29.059   grm.  =  10.0 
10  c.c.  =  0.29059   "    ;  0.100 
1  c.c.  =  0.029059  "     0.010 

Chlorine. 

1  c.c.  = :    0.029059     "  0.006068 

Sometimes  it  is  necessary  to  prove  the  accuracy  of  the  solu- 
tion by  standardizing  it  with  a  standard  solution  of  sodium 
chloride. 


58  NOTES  ON  CHEMICAL  LECTURES. 

Thus : 

1.0'grm.  Nad  is  dissolved  in  distilled  water  and  the  solution 
diluted  to  100  c.c. 

NaCl. 

100  c.c.  =  1.0       grm. 
10  c.c.  =  0.100     " 
1  c.c.  =  0.010     " 

Standardizing  the  argentic  nitrate  solution  :  To  10  c.c. 
of  the  NaCl  solution  two  drops  of  potassium  chromate  (K2CrO4) 
solution  (the  indicator),  are  added,  and  the  AgNO3  solution  run 
into  the  solution  from  a  burette  until  the  lemon-yellow  color 
of  the  liquid  is  changed  to  a  very  slight  orange-red.  The 
red  color  is  due  to  the  formation  of  red  argentic  chromate 
(Ag2CrO4),  and  indicates  that  all  of  the  NaCl  has  been  decom- 
posed and  a  slight  excess  of  the  AgNO3  solution  has  acted  on 
the  potassium  chromate  present. 

The  10  c.c.  of  NaCl  solution,  which  contains  0.100  grm.  of 
NaCl  should  require  exactly  10  c.c.  of  the  AgNO3  solution  to 
completely  precipitate  the  chlorine  and  act  upon  the  indicator 

a.  The  standard  solution  may  be  too  strong,  i.  e., — re- 
quiring the  addition  of  less  than  10  c.c.  of  the  AgNO3  to  the 
10  c.c.  of  solution  containing  0.100  grm.  NaCl.     It  may  be 
corrected  by  determining   and   adding  the  volume  of  water 
necessary  to  dilute  it  to  the  proper  strength. 

Suppose  8  c.c.  instead  of  10  c.c.  of  the  AgNO3  solution  have 
been  required  for  the  10  c.c.  of  solution  containing  0.100  grm. 
NaCl.  Then  to  every  8  c.c.  of  standard  solution  remaining 
a  volume  of  distilled  water  equal  to  the  difference  between  8 
and  10  c.c.,  or  2  c.c.  is  added. 

1000  c.c.  solution  prepared. 

8  c.c.  used. 
8)992  c.c.  on  hand. 

124  X  2  =  248  c.c.  water  to  be  added  to  the 
992  c.c.  standard  solution. 

10  c.c.  will  now  equal  0.100  grm.  of  NaCl. 
1  c.c.  "      0.010     "      "       " 

b.  The  standard  solution  may  be  too  weak,  i.  e., — requiring 
the  addition  of  more  than  10  c.c.  of  the  AgNO3  solution  to  the 


NOTES  ON  CHEMICAL  LECTURES.  59 

10  c.c.  of  solution  containing  0.100  grm.  NaCl.  The  AgNO3 
solution  may  be  corrected  by  adding  more  crystallized  AgNO3 
to  the  solution,  titering  with  10  c.c.  of  standard  NaCl  solution 
and  then  correcting  after  the  manner  of  the  correction  of  a 
standard  solution  that  is  too  strong  (see  a  before  mentioned). 

If  the  AgNO3  solution  is  thus  standardized  and  the  residue 
from  10  c.c.  urine  is  dissolved  in  .30  c.c.  water,  then,  in  actual 
analysis,  because  of  increased  dilution,  0.2  c.c.  must  be  deduc- 
ted (0.1  for  every  10  c.c.  above  a  fixed  10  c.c.)  from  the  num- 
ber of  c.c.  AgNO3  solution  required. 

c.  The  AgNO3  solution  may  be  standardized  so  that  in 
actual  analysis  no  correction  (deduction  of  0.2  c.c.)  will  be 
necessary. 

10  c.c.  standard  solution  of  NaCl  (containing  0.100  grm. 
NaCl)  are  diluted  with  20  c.c.  water,  so  that  the  volume  (30  c.c.) 
shall  equal  the  volume  of  the  final  solution  in  the  actual  work 
with  the  urine.  Two  drops  of  K2CrO4  solution  are  added  and 
the  AgNO3  solution  from  a  burette  is  run  into  the  NaCl  solu- 
tion until  the  lemon-yellow  color  of  the  liquid  is  changed  to  a 
slight  orange-red. 

If  more  or  less  than  10  c.c.  of  standard  AgNO3  solution 
should  be  required  to  give  the  reaction  with  the  indicator,  the 
AgNO3  solution  should  be  corrected,  after  the  manner  of  the 
correction  of  standard  solutions  that  are  too  weak  or  too  strong 
as  before  described,  so  that  exactly  10  c.c.  shall  be  required  for 
the  10  c.c.  of  standard  solution  of  NaCl  diluted  with  20  c.c.  of 
water. 

Method:  10  c.c.  of  urine,  to  which  is  added  about  2  grm. 
potassium  nitrate  (KNO3)  to  destroy  the  organic  matter,  are 
evaporated  to  dryness  in  a  small  porcelain  evaporating  dish 
on  a  water-bath  (absolute  dryness  cannot  be  obtained)  or  over 
a  flame,  care  being  taken  to  avoid  loss  from  spurting.  (The 
contents  of  the  dish  must  not  be  stirred.)  The  dish  con- 
taining the  residue  is  held  by  means  of  a  crucible  tongs  over 
a  flame  and  heated,  very  gently  at  first,  then  with  strong  heat 
until  all  of  the  organic  matter  is  destroyed  as  indicated  by  the 
disappearance  of  the  charred  material.  The  dish  containing 
the  residue,  while  cooling,  is  held  at  the  outer  edge  by  a  cruci- 
ble tongs  and  given  a  rotary  motion  until  the  fused  material 


60  NOTES  ON  CHEMICAL  LECTURES. 

has  distributed  itself  as  a  thin  layer  over  the  dish  and  finally 
solidified.  By  this  procedure  the  cracking  of  the  dish  will  be 
prevented.  Care  must  be  taken  that  in  this  procedure  none  of 
the  fused  material  comes  in  contact  with  the  crucible  tongs  or 
is  projected  from  the  dish.  When  the  dish  is  thoroughly 
cooled  the  residue  is  treated  with  5  c.c.  of  water  and  eight  or 
ten  drops  of  strong  nitric  acid.  The  nitric  acid  is  added  to 
neutralize  KOH  and  K2CO3  which  are  produced  in  the  decom- 
position of  the  KNO3  with  the  organic  matter.  The  liquid  in 
the  dish  is  warmed  to  hasten  solution.  This  first  portion  of 
5  c.c.  is  poured  into  a  beaker  (disregarding  any  enamel  which 
may  have  separated  from  the  dish),  and  washing  the  dish  with 
portions  of  5  c.c.  of  water  is  repeated  (without  further  addition 
of  nitric  acid),  heating,  if  necessary,  until  the  dish  has  been 
thoroughly  washed.  Each  portion  of  5  c.c.  is  poured  into  the 
beaker  until  30  c.c.  have  been  employed  and  collected  in  the 
beaker.  If  the  liquid  is  not  acid  in  reaction  it  must  be  veiy 
slightly  acidulated  with  nitric  acid.  (Up  to  this  point,  ex- 
cept disregarding  the  enamel,  the  method  is  practically  similar 
to  the  one  employed  in  the  gravimetric  determination  of 
sodium  chloride). 

The  liquid  is  neutralized  by  the  addition  of  an  excess  of 
precipitated  calcium  carbonate  (CaCO3).  The  point  of  neu- 
tralization is  determined  by  the  cessation  of  effervescence  and 
the  remaining  of  a  portion  of  undecomposed  calcium  carbonate 
at  the  bottom  of  the  beaker.  (Neutralization  of  the  solution 
is  necessary  because  the  nitric  acid  present  would  dissolve  the 
orange-red  argentic  chromate  produced,  and  thus  prevent  a 
visible  reaction  on  the  indicator). 

Two  drops  of  solution  of  potassium  chromate  (the  indicator) 
are  added  and  the  standard  solution  of  AgNO3  is  run  from  the 
burette  into  the  30  c.c.  of  liquid  containing  the  sodium  chloride 
until  the  lemon-yellow  color  of  the  liquid  is  changed  to  a 
slight  orange-red. 

The  number  of  cubic  centimetres  of  standard  AgNO3  solution 
required  is  read  off  and  this  number  is  multiplied  by  the  value 
of  1  c.c.  of  the  standard  AgNO3  solution  expressed  in  terms  of 
NaCl, — namely,  0.010.  The  result  obtained  is  multiplied  by 
10  in  order  to  obtain  the  percentage  of  NaCl  in  the  urine. 


NOTES  ON  CHEMICAL  LECTURES.  61 

If  the  standard  AgNO3  solution  has  been  standardized  with 
10  c.c.  of  standard  NaCl  solution  diluted  with  20  c.c.  of  water 
making  a  volume  of  30  c.c.  no  correction  is  necessary. 

Example :  Suppose  8.3  c.c.  AgNO3  solution  have  been 
required.  Then  8.3  X  0.010  =  0.083  grm.  NaCl  in  the  10  c.c. 
urine  employed.  0.083  X  10  =  0.83  per  cent.  NaCl. 

3.  Liebig's  method  for  the  determination  of  sodium  chloride :  Depends 
upon  the  formation  of  a  soluble  salt  of  mercury  (mercuric  chloride,  HgCl2)  on  the 
addition  of  mercuric  nitrate,  Hg(NO3)2,  to  a  solution  of  sodium  chloride. 

117. 
2NaCl  -  Hg(NO3).,  =  HgCI2  +  2NaNO3 

Liebig's  method  for  the  determination  of  NaCl  in  the  urine  is  not  accurate  and 
is  rarely  used. 

The  mercuric  nitrate  solution  is  prepaied  of  such  strength  that  1  c.c.  of  it  shall 
equal  0.010  grm.  NaCl. 

117  grm.  NaCl  require  200  grm.  of  mercury  (once  the  atomic  weight  of  Hg 
expressed  in  grammes). 

Hence 

2NaCl.     Hg.       NaCl.      Hg. 

117  :  200  ::  10  :  17.094  grm. 

Or,  117  grm.  NaCl  require  216  grm.  mercuric  oxide  (HgO)  (once  the  molecular 
weight  of  HgO  expressed  in  grammes). 

2NaCl.     HgO.      NaCl.      HgO. 

117    :   216  ::  10  :  18.461  grm. 

17.094  grm.  of  metallic  mercury,  or  18.461  grm.  of  mercuric  oxide,  are  equal  to 
10  grm.  NaCl. 

Preparation  of  standard  solution  of  mercuric  nitrate  :  17.094  grm.  of 
mercury,  or  18.461  grm.  of  mercuric  oxide,  are  dissolved  in  an  excess  cf  nitric 
acid  to  which  is  added  a  small  quantity  of  water.  The  excess  of  acid  is  expelled 
by  evaporation  and  the  residue  is  dissolved  in  distilled  water  and  slowly  diluted 
to  1000  c.c.  If  on  dilution  with  water  a  canary-yellow  precipitate  of  basic 
mercuric  nitrate  should  separate,  it  is  allowed  to  subside,  the  supernatant  liquid  is 
poured  off  and  the  precipitate  is  dissolved  in  a  few  drops  of  strong  nitric  acid,  and 
the  solution  returned  to  the  previously  poured  off  supernatant  liquid. 

Hg(N03),,  sol.       NaCl. 
1000  c.c.  ==  10  0          grm. 
10  c.c.  =  0  100 
1  c.c.  =  0  010  " 

Chlrrine. 

1  c.c.  =  0.006068    " 

The  mercuric  nitrate  solution  may  be  standardized  with  a  solution  of  NaCl  con- 
taining 1.0  grm.  NaCl  in  100  c.c.  water,  using  a  pinch  of  urea  as  the  indicator. 


62  NOTES  ON  CHEMICAL  LECTURES. 

The  phosphates,  sulphates^and  carbonates  in  the  urine  inttrfere  with  the  appli- 
cation of  the  method.  They  are  removed  by  the  baryta  mixture,  composed  of 

2  volumes  of  a  cold  saturated  solution  of  barium  hydroxide  (Ba(OH)2). 
1  volume  of  a  cold  saturated  solution  of  barium  nitrate  (Ba(NO3)2). 

The  first  action  of  the  mercuric  solution  will  be  on  the  NaCl  in  the  urine  to 
form  soluble  HgCl2 ;  as  soon  as  all  the  NaCl  present  has  been  decomposed,  any 
excess  of  mercuric  nitrate  solution  added  will  act  upon  the  urea  to  form  a  white 
insoluble  compound  of  mercuric  oxide  and  urea,  (HgO)2CO(NH2)2, 

2Hg(N03)2  +  CO(NH2)2  +  2H20  =  (HgO)2CO(NH2)2  +  4HNO3 

and  thus  the  urea  acts  as  the  indicator. 

Method  :  40  c.c.  of  urine  are  mixed  with  20  c.c.  of  baryta  mixture  and  filtered 
through  a  filter  that  has  not  been  previously  moistened  with  water.  The  filtrate 
is  neutralized  with  a  drop  or  two  of  nitric  acid.  15  c.c.  of  the  filtrate  (representing 
10  c.c.  of  urine  and  5  c.c.  of  baryta  mixture)  are  transferred  by  means  of  a  pipette 
to  a  beaker.  The  standard  mercuric  nitrate  solution  is  run  from  the  burette  into 
the  liquid  until  a  permanent  milky;  turbidity  is  produced.  (Action  on  the  urea.) 

The  number  of  cubic  centimetres  of  standard  mercuric  nitrate  solution  required 
is  multiplied  by  0.010  and  the  result  multiplied  by  10  furnishes  the  percentage  of 
NaCl  in  the  urine. 

UREA  (Carbamide). 

CO(NH2)2.     Molec.  wt.,  60. 

CON2H4,  urea.  Generally  considered  to  be  CO(NH2)2, 
carbamide.  Gamgee  considers  that  it  is  not  carbamide,  be- 
cause, when  urea  is  heated  with  potassium  permanganate 
(K2Mn2O8)  and  potassium  hydroxide,  all  of  its  nitrogen  is 
evolved  as  free  nitrogen,  whereas  salts  of  ammonium  (NH4) 
and  amides  yield  their  nitrogen  as  N2O5: 

Compounds  isomeric  with  urea  : 

NH4CNO,  ammonium  cyanate. 
CON2H4,  isuretin. 

Isuretin,  CON2H4,  is  not  urea,  because  it  is 

NH 
NH2OH    +    HCN  =  CH  NH,    hydroxyl-methenyldiamide. 

Hydroxylamide.     Hydrocyanic  acid.  OFT 

Urea  was  first  recognized  in  the  urine,  and  obtained  in  an 
impure  state,  by  Rouelle,  in  1773.  It  was  obtained  in  a  purer 
condition,  by  Fourcroy  and  Vauquelin,  in  1799.  It  was  pre- 
pared artificially,  by  Woehler,  in  J  828,  it  being  the  first  organic 
compound  produced  artificially. 


NOTES  ON  CHEMICAL  LECTURES.  63 

Urea  is  found  in  the  urine  of  all  mammals.  The  urine  of 
birds  and  reptiles  contains  it  in  small  quantity.  Thirty  per 
cent,  of  the  solid  matter  of  the  vitreous  humor  of  the  eye  is 
urea.  It  is  contained  in  almost  all  the  animal  fluids, — blood, 
lymph,  chyle,  etc., — and  in  the  liver  and  spleen.  It  is  the 
principal  solid  constituent  of  the  urine.  Ninety  per  cent,  of  the 
nitrogen  eliminated  by  the  urine  is  in  the  form  of  urea. 

Urea  may  be  prepared  artificially  by  fusing  and  oxidizing 
potassium  ferrocyanide  (K4Fe(CN)6)  with  manganese  dioxide 
(MnO2)  or  with  minium  (Pb3O4  =  2PbO  +  PbO2),  with  the 
production  of  potassium  cyanate  (KCNO),  which,  when  warmed 
with  a  solution  of  ammonium  sulphate  ((NH4)2SO4),  forms 
ammonium  cyanate  (NH4CNO),  and  by  continued  warming 
changes  into  urea  (CO(NH2)2).  The  solution  is  evaporated  to 
dryness  on  a  water-bath,  and  the  residue  extracted  with 
strong  alcohol.  The  alcohol  dissolves  only  the  urea,  which 
may  be  obtained  in  crystalline  form  by  allowing  the  alcohol  to 
evaporate  at  ordinary  temperature. 

1.  K4Fe(CN)6  +  O9  =  4KCNO  +  2CO2  +  FeO  +  N2 

2.  2KCNO  +  (NH4)2SO4  =  2NH4CNO  +  K2SO4 

3.  NH4CNO  =  CO(NH2)2 

It  may  also  be  prepared  by  warming  plumbic  cyanate 
(Pb(CNO)2)  with  a  solution  of  ammonium  sulphate, 

Pb(CNO)2  +  (NH4)2SO4  =  PbSO4  +  2NH4CNO 
on  further  warming,  the  NH4CNO  is  converted  into  urea. 

UREA  MAY  BE  OBTAINED  FROM  THE  URINE  BY  THE 
FOLLOWING  METHODS. 

1.  As  urea  :  Baryta  mixture  is  added  to  the  urine,  the  liquid 
is  filtered  and  the  filtrate  is  evaporated  to  dryness  on  a  water- 
bath.  The  residue  is  treated  with  strong  alcohol  and  the  solu- 
tion filtered  and  evaporated  to  dryness.  The  residue  is  dissolved 
in  water  and  the  solution  decolorized  by  being  passed  through 
animal  charcoal.  The  decolorized  liquid  is  evaporated  to  dry- 
ness  and  the  residue  treated  with  strong  alcohol  and  the  liquid 
filtered.  The  filtrate  is  allowed  to  evaporate  at  ordinary  tem- 
perature, and  needle-like  crystals  of  urea  will  separate 


64  NOTES  ON  CHEMICAL  LECTURES. 

2.  As  urea  nitrate  :   (soluble  in  8  parts  of  water).     250  c.c., 
or  more,  of  urine  are  evaporated  on  a  water-bath  to  about 
one-sixth  its  original  volume.     When  cold,  nitric  acid,  of  about 
1.25  specific  gravity,  is  added  to  the  liquid  and  the  mixture 
kept  cold.     Crystals  of  CO(NH2)2HNO3  will  separate.     The 
mass  of  crystals  is  collected  on  a  moistened  piece  of  muslin 
and  the  excess  of  liquid  squeezed  out.     The  mass  is  scraped 
off  the  muslin   and    dissolved   in    water.     Barium   carbonate 
(BaCO3)  is  added  to  the  solution  to  separate  the  HNO3  from 
the  CO(NH2)2HNO3 

2CO(NH2)2HNO3  +  BaCO3  =  Ba(NO3)2  +  H2O  +  CO2  + 
2CO(NH2)2 

The  solution  is  decolorized  by  being  passed  through  animal 
charcoal.  The  decolorized  liquid  is  evaporated  to  dryness  on 
a  water-bath,  the  residue  is  treated  with  strong  alcohol  and  the 
liquid  is  filtered,  and  the  filtrate  allowed  to  evaporate  at  ordi- 
dinary  temperature.  Crystals  of  urea  will  separate. 

3.  As  urea  oxalate  :  (soluble  in  25  parts  of  water).     The 
method  is  similar  to  that  with  nitric  acid  except  that  oxalic 
acid  (H2C2O4)  (strong  solution  or  in  powder)  is  used  instead  of 
nitric  acid,  and  calcium  carbonate  (CaCO3)  is  used  instead  of 
barium  carbonate. 

(CO(NH2)2)2H2C2O4  +  CaCO3  =  CaC2O4  +  H2O  +  CO2 

Urea  oxalate.  Calcium  oxalate. 

+  2CO(NH2)2 

Properties  of  urea :  Urea  is  a  white,  odorless  compound, 
crystallizing  in  four-sided  prisms.  It  has  a  cooling,  bitter-like 
taste,  somewhat  resembling  potassium  nitrate.  It  is  very 
soluble  in  water,  1  in  1  ;  soluble  in  alcohol,  1  in  5 ;  insoluble 
in  ether.  Melts  at  a  temperature  of  130°  C. 

Urea  in  solution  has  no  action  on  blue  or  red  litmus-paper, 
is  neutral,  yet  it  will  combine  with  acids,  bases,  and  salts. 

a.  CO(NH2)2HNO3 

b.  (HgO)2CO(NH2)2 

c.  CO(NH2)2NaCl 

It  unites  with  acids  without  displacing  the  hydrogen  in  the 
acid. 


NOTES  ON  CHEMICAL  LECTURES.  65 

a.  Urea  in  solution  is  decomposed  by  sodium  hypochlorite 
with  the  evolution  of  CO2  and  N. 

CO(NH2)2  +  SNaCIO  =  3NaCl  +  2H2O  +  CO2  +  N2 

b.  Urea  in  solution  is  decomposed  by  nitrous  acid  (HNO2) 
with  the  evolution  of  CO9  and  N. 


CO(NH,)2  +  2HNO2  =  3H2O  -f  CO2  +  2N 


c.  Urea  heated  with  water  in  a  glass  tube  sealed  at  both 
ends  is  converted  into  ammonium  carbonate. 

CO(NH2)2  +  2H2O  =  (NH4)2CO3 

A  like  conversion  occurs  when  urea  in  solution  is  exposed 
for  a  time  to  the  air,  due  to  the  action  of  micrococcus  ureae. 

a.  Urea  in  crystals  heated  to  a  temperature  of  150°— 170° 
C.  fuses  and  yields  ammonia  (NH3)  and  a  compound  called 
biuret  (C2H5N3O2). 

2CO(NH2)2  =  C2H5N3O2  +  NH3 

Biuret  in  solution  produces  a  violet-red  color  on  the  addi- 
tion of  a  few  drops  of  very  dilute  cupric  sulphate  solution, 
and  afterwards  a  solution  of  potassium  or  sodium  hydroxide. 
(Biuret  reaction.) 

Peptones  and  albumoses  respond  to  the  same  test. 

b.  Urea  heated   to  a  higher  temperature  (over   170°    C.) 
yields  ammonia  NH3,  and  cyanuric  acid  (II3C3N3O3). 

3CO(NH2)2  =  3NH,  +  H3C3N3O3 

c.  Urea  heated  to  a  still   higher  temperature    yields    am- 
monia, and  melanuric  acid,  H4C3N4O2. 

4CO(NH2)2  =  4NH3  -f  CO2  -f-  H4C3N4O2 
QUANTITATIVE  DETERMINATION  OF  UREA  IN  URINE. 

1.  Davy's  method,  introduced  in  1854,  depends  upon  the  decomposition  of 
the  urea  in  the  urine  by  means  of  sodium  hypochlorite  with  the  evolution  of  carbon 
dioxide  and  nitrogen.  The  CO.,  is  ahsor'ied  by  the  excess  of  alkali  (NaOH)  in 
the  NaCIO  solution,  the  nitrogen  remains  unabsorbed,  and  is  collected,  and  meas- 
ured in  a  tube  graduated  in  cubic  inches. 

Davy's  method  is  inaccurate,  is  of  historical  interest  only  and  is  not  used. 


66  NOTES  ON  CHEMICAL  LECTURES. 

The  volume  of  nitrogen  is  corrected  for  temperature  (60°  F.)  and  barometric 
pressure  (30  inches),  and  the  quantity  of  urea  calculated  from  the  volume  of 
nitrogen  obtained. 

60.  2s. 

CO(NH2)2  -f  SNaCIO  =  3NaCl  +  2H2O  +  CO2  +  N2 

1  molecule  (60)  of  urea  contains  two  atoms  (2  X  14  •=  28)  of  nitrogen. 
28  grains  N  =  93.33  cubic  inches. 

60  grains  urea  contain  28  grains  N  =  93.33  cubic  inches  nitrogen,  at  temperature 
of  60°  F.  and  barometric  pressure  of  30  inches. 

Grains  urea.        Cubic  inches.        Grain  urea.        Nitrogen. 

60        :         93.33        ::        1        :       1.55  cu.  in. 

Consequently  1.55  cubic  inch  of  nitrogen  is  evolved  from  1  grain  of  urea,  or  1 
cubic  inch  of  nitrogen  is  evolved  from  0.645  grain  of  urea. 
Cu.  in.  N.        Grain  urea.        Cu.  in  N.        Urea. 

1.55       :       1       ::       1     :     0.645  grain. 

Method :  A  tube  graduated  in  cubic  inches  is  filled  with  mercury  to  one  third 
of  its  capacity.  100  grains  of  urine  are  added  and  the  remainder  of  the  tube  is 
rapidly  filled  with  sodium  hypochlorite  solution.  The  thumb  is  quickly  placed 
over  the  opening  of  ihe  tube  and  the  latter  is  inverted  in  a  trough  containing 
mercury.  Decomposition  of  the  urea  occurs  and  the  evolved  nitrogen  collects  in 
the  upper  part  of  the  tube. 

After  the  lapse  of  about  half  an  hour  the  opening  of  the  tube  is  closed  with  the 
thumb  and  the  tube  transferred  to  a  vessel  containing  water.  The  atmospheric 
pressure  is  equalized  and  the  number  of  cubic  inches  of  nitrogen  evolved  is  read 
off.  The  number  of  cubic  inches  of  nitrogen  evolved  is  divided  by  1.55  or  multi- 
plied by  0  645,  and  the  result  will  be  the  percentage  of  urea  in  the  urine.  (100 
grains  of  urine  having  been  employed.) 

Suppose  4.65  cubic  inches  nitrogen  evolved. 

4.65  -5- 1.55  -=  3  per  cent.  urea. 
Or,  4.65  X  0-645  —  2.99  per  cent.  (3  per  cent.)  urea. 

Objections  to  this  method :  According  to  Fenton,  NaCIO  in  presence  of 
caustic  alkalies  causes  the  evolution  of  only  one-half  of  the  nitrogen  of  urea,  the 
remainder  being  retained  as  cyanate,  thus  : 

2CO(NH2)2  +  SNaCIO  +  2NaOH  =  3  NaCl  +  2NaCNO  +  5H2O  +  N2 

2.  Fowler's  modification  of  Davy's  method  for  the  determination  of  urea  : 
Depends  upon  the  decomposition  of  urea  in  solution  by  sodium  hypochlorite 
(NaCIO),  thereby  causing  a  reduction  in  the  density  of  the  solution.  Fowler 
found  that  a  loss  of  one  degree  in  specific  gravity  in  a  mixture  of  one  volume  of 
urine  and  seven  volumes  of  hypochlorite  solution  represented  the  presence  (decom- 
position) of  0.77  per  cent,  of  urea. 

Seven  volumes  of  hypochlorite  solution  of  1035  specific  gravity  will  decompose 
the  urea  in  one  volume  of  an  average  urine. 

The  method  is  inaccurate  and  is  rarely  used. 

Method :  The  specific  gravities  of  the  urine  and  of  the  hypochlorite  solution 
are  determined  separately.  To  one  volume  of  the  urine  seven  volumes  of  hypo- 
chlorite solution  are  added, — say  10  c.c.  urine  and  70  c.c.  hypochlorite  solution. 


NOTES  ON  CHEMICAL  LECTURES.  67 

(The  specific  gravity  of  this  mixture  is  determined  by  calculation.)  After  allowing 
the  mixture  to  stand  umil  the  decomposition  is  completed  ^ about  half  an  hour)  the 
specific  gravity  of  the  mixture  is  determined.  This  latter  specific  gravity  is  deducted 
from  the  specific  gravity  (obtained  by  calculation)  of  the  mixture.  The  loss  of 
specific  gravity  multiplied  by  0.77  furnishes  the  percentage  of  urea  in  the  urine. 
Example  : 

7  volumes  of  NaCIO  sol.,  specific  gravity    .    .    .    1036  X  7  =  7252 
1  volume  of  urine,  "  "         ...    1025  X  1  =  1025 

8  volumes 8)8277 

Specific  gravity  of  mixture  before   decomposition  .    .          1034.6 
"  "  "        after  "  .    .         1030.0 

4.6 

Hence  4.6  X  0.77  --=  3.524  per  cent.  urea. 

3.  Hypobromite  method  for  the  quantitative  determination 
of  urea :  Depends  upon  the  decomposition  of  the  urea  in  the 
urine  by  means  of  sodium  hypobromite  (NaBrO)  with  the 
production  of  sodium  bromide  (NaBr),  water,  carbon  dioxide 
(CO2),  and  the  evolution  of  nitrogen. 

This  is  the  most  accurate  method  for  the  quantitative  deter- 
mination of  urea. 

The  CO2  is  absorbed  by  the  excess  of  alkali  (NaOH)  in  the 
NaBrO  solution,  and  the  nitrogen  remains  unabsorbed,  and  is 
collected,  and  measured  in  a  tube  graduated  in  cubic  centi- 
metres. 

The  volume  of  nitrogen  is  corrected  for  temperature  (0°  C.) 
and  barometric  pressure  (760  mm.),  and  the  quantity  of  urea 
is  calculated  from  the  volume  of  nitrogen  obtained. 

60.  28. 

CO(NH2)2  +  3NaBrO  ==  3NaBr  +  2H2O  +  CO2  +  N2 

1  molecule  urea.     1  molecule  (2  atoms). 
60.  28. 

CO(NH2)2     =     N2 

00  grammes  of  urea  contain  28  grar^mes  nitrogen. 
28  grammes  nitrogen  =  22.32  litres  or  22320  c.c. 

60  grammes  urea  evolve  22.32  22320  c.c.  nitrogen. 

Grms.  urea.     Grm.  urea.  Litres.  Litre. 

60     :      1      ::      22.32    :    0.372  or  372  cubic  centimetres. 

1  gramme  of  urea  will  evolve  372  c.c.  of  nitrogen  (at  0°  C. 
and  760  mm.).  2. 

c.c.  N      Grm.  urea,     c  c.  N.          Grm.  urea. 

372        1  1     :    0.002688 


68  A'OTES  ON  CHEMICAL  LECTURES. 

1  cubic  centimetre  of  nitrogen,  measured  at  0°  C.  temper- 
ature and  760  mm.  pressure,  is  evolved  from  0.002688  grm. 
urea  (2.688  milligrammes  urea). 

1.0      gramme  urea  evolves  372.0      c.c.  nitrogen. 
0.001  "  0.372    " 

0.010  "          "          3.72      " 

0.020        "          "          "          7.44      "        "' 
0.030  "        11.16      " 

1  c.c.  of  a  1  per  cent,  solution  of  urea  (containing  0.010 
urea)  will  evolve  3.72  c.c.  nitrogen. 

1  c.c.  of  a  2  per  cent,  solution  of  urea  (containing  0.020 
urea)  will  evolve  7.44  c.c.  nitrogen. 

The  sodium  hypobromite  solution  is  prepared  by  dissolv- 
ing 100  grammes  sodium  hydroxide  (NaOH)  in  250  c.c.  water, 
cooling  the  solution,  an^  adding  25  c.c  (75  grammes)  of 
bromine.  f 

The  reagent  (NaBriB^lution)  should  be  freshly  prepared. 


160.  80. 


2Br  +  2NaOlt'pj 

2Br.         2NaOH.J 

160        80 


Hence  the  75  grammes  OT 


NaBr  +  HO 


rm.  Br.          NaOH. 


75    :     37.5  grm. 
v.  " 


bromine  will  combine  with  only 
37.5  grammes  of  the  100  grammes  of  NaOH  employed  in  the 
preparation  of  the  solution,  leaving  the  difference  between 
37.5  and  100,  or  62.5  grammes,  free  NaOH  in  the  solution,  to 
absorb  the  CO2  evolved  in  the  application  of  the  method. 

There  are  many  forms  of  apparatus  employed  in  the  deter- 
mination of  urea  by  sodium  hypobromite, — 

Russell  &  West's. 
Huefner's. 
Greene's. 
Marshall's. 
Etc. 

Method,  with  the  use  of  Marshall's  apparatus  :  The  side 
opening  of  the  bulbed  tube  is  closed  with  the  thumb  and  the 
tube  is  filled  with  hypobromite  solution  (which  may  previously 
be  diluted  with  an  equal  volume  of  distilled  water).  The  upper 


.VOTES  ON  CHEMICAL  LECTURES.  09 

opening  of  the  tube  is  closed  with  a  rubber  stopper  and  the 
tube  is  inclined  so  as  to  allow  any  air-bubbles  which  may  be 
just  below  the  rubber  stopper  to  escape  through  the  side 
opening.  The  tube  is  inverted  and  the  end  closed  with  the 
rubber  stopper  is  fixed  in  the  saucer-shaped  vessel. 

1  c.c.  of  the  urine  is  slowly  run  from  the  graduated  pipette 
through  the  side  opening  of  the  tube  into  the  hypobromite 
solution,  and  the  pipette  quickly  withdrawn. 

1  c.c.  of  urine,  in  the  great  majority  of  cases,  suffices;  if, 
however,  the  urine  contain  very  little  urea,  more  than  1  c.c. 
may  be  employed. 

When  the  decomposition  is  completed  (about  twenty  min- 
utes) and  all  the  gas-bubbles  have  collected  in  the  upper  part 
of  the  tube  (may  be  facilitated  by  gently  tapping  the  tube 
with  the  finger),  the  atmospheric  pressure  is  equalized  by 
attaching  the  funnel-tube  to  the  side  opening  of  the  hypo- 
bromite tube,  and  pouring  hypobromite  solution  into  it  until 
the  surfaces  of  the  liquid  in  both  tubes  are  equal  in  height. 
The  number  of  cubic  centimetres  of  nitrogen  is  read  off,  the 
temperature  of  the  air  and  the  barometric  pressure  are  ob- 
served and  the  amount  of  urea  calculated  from  the  volume  of 
nitrogen  evolved  after  having  been  corrected  for  temperature 
and  pressure. 

Example  :  Suppose  1  c.c.  urine  evoived  12.5  c.c.  nitrogen, 
the  temperature  being  20°  C.  and  barometric  pressure  750  mm. 

A.  Then,  correcting  simply  for  temperature  and  pres- 
sure :  $  v  . 

20°.  0°.  20°. 

a.  293  :  273  ::   J2.5  :  11.64  c.c.  at  0°  C.  temp. 
and,  p  y          y< 

b.  760  :  750  ::  11.64  :  11.48  c.c.  at  0°  C.temp.  and  760  mm. 
Hence 


11.48  c.c.  N  X  O.OQ2688  =  0.03085  urea  (in  1  c.c.  urine). 
0.03085  X  100  =  3.085  per  cent,  urea  (in  100  c.c.  urine). 

B.  Correcting  for  temperature,  pressure  and  tension  of 
aqueous  vapor  : 

20°.  0°.  20°. 

a.  293  :  273   ::   i2.5  :  11.64  c.c.  at  0°  C.  temp. 


70  NOTES  ON  CHEMICAL  LECTURES. 

b.  750.0  mm.  observed  barometric  pressure, 

1 7.4  correc.  in  mm.  for  tension  of  aqueous  vapor  at  20°  C. 
732.6  mm.  corrected  barometric  pressure. 

760  :    732.6    ::    11.64  :  11.23  c.c.  at  0°  C.  temp.  760  mm. 
pressure  and  corrected  for  tension  of  aqueous  vapor. 
Hence 

11.23  c.c.  N  X  0.002688  =  0.03018  urea  (in  1  c.c.  urine). 
0.03018  X  100  =  3.018  per  cent,  urea  (in  100  c.c.  urine). 

C.  Correcting  for  temperature,  barometric  pressure,  and 
tension  of  aqueous  vapor  using  the  following  formula : 


V'  = 


v  X  (B-T) 


760  X  (1  +  0.003665  1) 
in  which 

V  is  the  corrected  volume  of  nitrogen  in  c.c. 

v        "       observed 

B       "      barometric  pressure  in  mm. 

T       "      tension  of  aqueous  vapor  for  temp.  t. 

t        "      observed  temperature. 

0.003665  is  the  coefficient  of  expansion  of  gases  for  each 
degree  Centigrade. 

Hence,  for  the  above  example, 


12.5  X  (750  —  17.4)  _  12.5  X  732.6       9157.50 


760  X  1.073  760  X  1.073          815.48 


^  n  93     ~ 

~~ 


11.23  c.c.  N  X  0.002688  =  0.03018  (in  1  c.c.  urine). 
0.03018  X  100  =  3.018  per  cent,  urea  (in  100  c.c.  urine). 

D.  To  correct  for  the  expansion  of  mercury  at  20°  C.  in  the  barometer-  tube, 

0.000171  X  t° 
thus,  0.000171  X    20  =  0.0034 

0.0034  X  750  =  2.56  mm. 
so, 

Barom.  =  750  —  2  56  =  747.44. 

750:747.44  ::  11.23  :  11.19  c.c.  N. 

11.19  X  0.002688  =  0.03007  grm.  urea. 

0.03007  X  100  =  3  007  per  cent,  urea  (in  100  c.c.  urine). 


NOTES  ON  CHEMICAL  LECTURES.  71 

Table  of  Tension  of  Aqueous  Vapor  Expressed  in  Millimetres  for 
Certain  Temperatures  Centigrade. 


Temp.  Temp. 


Tension  rp  Tension 

in  mm.  in  mm. 

10°  C 9.139  23°  C 20.857 

11°C 9.767  24°  C 22.152 

12°  C 10.432  25°  C 23.517 

13°  C 11.137  26°  C 24.955 

14°  C 11.883  27°  C 26.470 

15°  C 12.673  28°  C 28.065 

16°  C 13.510  29°  C 29.743 

17°  C 14,395  30°  C 31.509 

18°  C.  .......  15.330  31°  C 33.366 

19°  C 16.318  3i°  C 35.318 

20°  C 17.363  33°  C 37.368 

21°  C 18.465  34°  C 39.522 

22°  C 19.629  35°  C 41.784 

4.  Liebig's  method  for  the  quantitative  determination  of 
urea  :  Depends  upon  the  production  of  an  insoluble  compound 
of  mercuric  oxide  and  urea  (HgO)2CO(NH2)2  on  the  addition 
of  mercuric  nitrate  Hg(NO3).,  to  a  solution  of  urea. 

q?,VlOj±-l,vla*jl.     -  H-j  tf i-h  2.  +1  Co  *T.  Oj 

2Hg(N03)2+CO(NH2)2^2H20  =  (HgO)2CO(NH2)2+4HN03 

In  the  practical  application  of  the  method  the  Hg(NO3)2 
acts  first  on  the  NaCl  of  the  urine  to  form  soluble  HgCL. 
When  sufficient  Hg(NO3)2  has  been  added  to  combine  with  all 
the  NaCl  present  it  then  acts  on  the  urea. 


Hg(NO3)2  +  2NaCl  =  HgCl._,  +  2NaNO 


The  precipitate  formed  after  the  NaCl  is  satisfied  is  com- 
posed of  2  molecules  of  HgO  in  combination  with  1  molecule 
of  CO(NH2)2. 

216. 

Twice  the  molecular  weight  of  HgO  is  432 

Once     "  "        "    CO(NH2)2  "    60 

In  the  formation  of  the  compound  (HgO)2CO(NH2)2,  432 
parts  by  weight  of  HgO  enter  into  combination  with  60  parts 
by  weight  of  CO(NH2)2. 


72  NOTES  ON  CHEMICAL  LECTURES. 

Preparation  of  the  standard  Hg(NO3)2  solution;  The 
quantity  of  HgO  necessary  to  prepare  1000  c.c.  of  standard 
Hg(NO3)2  solution  so  that  1  c.c.  of  it  shall  equal  0.010  urea, 
is  determined  by 

Urea.          HgO.  Urea.  HgO. 

60   :   432    ::    10   :    72.0  grm.  =  66.66  grm.  metallic  Hg. 

In  the  preparation  of  the  solution  5.2  grm.  HgO  must  be 
added  to  the  72.0  grm.  to  act  on  the  indicator. 

72.0  +  5.2  —  77.2  grm.  HgO  =  71.48  grm.  metallic  Hg. 
Hence 

1000  c.c.  containing  77.2    grm.  HgO  =  10.0    grm.  urea. 
1  c.c.         "  0.0772  "        "      =    0.010  " 

This  same  solution  may  be  used  for  the  quantitative  deter- 
mination of  sodium  chloride. 

HgO.         2NaCl.  HgO.  NaCl. 

216    :    117    ::    77.2   :   41.817  grm. 

NaCl. 

1000  c.c.  containing  77.2    grm.  HgO  =  41.817         grm. 
1  c.c.         "  0.0772"       "      =    0.041817      " 

The  insoluble  HgO,  or  the  metallic  Hg,  is  converted  into 
soluble  Hg(NO3)2  by  dissolving  in  nitric  acid. 

77.2  grm.  HgO  or  71.48  grm.  metallic  Hg  are  dissolved  in 
an  excess  of  nitric  acid  to  which  is  added  a  small  quantity  of 
water.  The  excess  of  acid  is  expelled  by  evaporation  on  a 
sand-bath  and  the  residue  is  dissolved  in  distilled  water,  and 
slowly  diluted  to  a  volume  of  900  c.c.  If  on  dilution  with 
water  a  canary-yellow  precipitate  of  basic  mercuric  nitrate 
should  separate,  it  is  allowed  to  subside,  the  supernatant  liquid 
is  poured  off  and  reserved.  The  canary-yellow  precipitate  is 
dissolved  in  a  few  drops  of  strong  nitric  acid  and  the  solution 
returned  to  the  previously  poured  off  supernatant  liquid. 
Should  there  be  a  recurrence  of  the  precipitation,  the  precipi- 
tate must  be  allowed  to  subside,  the  supernatant  liquid  poured 
off,  etc.,  as  above  described. 

The  mercuric  nitrate  solution  must  be  standardized  with  a 
standard  solution  of  urea  of  2  per  cent,  strength. 


0 


NOTES  ON  CHEMICAL  LECTURES.  73 

Preparation  of  the  standard  urea  solution  :  2.0  grm.  dry 
urea  are  dissolved  in  distilled  water  and  the  solution  is  diluted 
to  100  c.c. 

Urea. 

100  c.c.  =  2.0      grm. 

10  c.c.  =  0.200     " 

1  c.c.  =  0.020     " 

The  indicator  is  a  strong  solution  of  sodium  carbonate. 
With  mercuric  nitrate  it  produces  yellowish-brown  basic 
mercuric  oxycarbonate,  HgCO3(HgO)3. 

4Hg(NO3)2  +  4Na2CO3  =  HgCO3(HgO)3  +  8NaNO3  +  3CO2 

Standardizing  the  mercuric  nitrate  solution  :  To  stand- 
ardize the  mercuric  nitrate  solution,  10  c.c.  of  the  standard 
urea  solution  (==  0.200  urea)  are  placed  in  a  beaker,  and  the 
mercuric  nitrate  solution  is  run  into  it  from  a  burette,  stirring 
after  each  addition,  until  a  drop  of  the  liquid  in  the  beaker 
produces  a  slight  yellow  color  when  brought,  by  means  of  a 
glass  rod,  in  contact  with  sodium  carbonate  solution  on  a 
porcelain  tablet. 

If  1  c.c.  of  the  mercuric  nitrate  solution  is  equal  to  0.010 
urea,  then  20  c.c.  should  be  required  to  combine  with  the  urea 
(0.200)  present  in  the  10  c.c.  urea  solution  and  act  on  the 
indicator. 

1000  c.c.  contains  5.2        grm.  HgO  to  act  on  the  indicator. 
1  c.c.         "       0.0052     "  " 

20  c.c.  HgO  solution  having  been  required  for  the  10  c.c. 
urea  solution,  and  as  each  c.c.  HgO  solution  contains  0.0052 
HgO  to  act  on  the  indicator,  20  X  0.0052  or  0.104  HgO  must 
have  been  added  with  the  20  c.c.  HgO  solution  to  the  10  c.c. 
urea  solution.  Hence,  in  the  combined  volumes,  20  c.c.  -f-  10 
c.c.  =  30  c.c.,  there  were  present  0.104  HgO,  and  in  each  c.c. 
0.104  -r-  30  =  0.003466  mgrm.  HgO  to  act  on  the  indicator. 

If  a  larger  or  smaller  quantity  than  20  c.c.  should  be 
required,  the  mercuric  nitrate  solution  must  be  corrected  after 
the  manner  given  for  solutions  too  strong  or  too  weak  in  the 
correction  of  the  argentic  nitrate  solution  for  the  determination 
of  sodium  chloride. 


74  NOTES  ON  CHEMICAL  LECTURES. 

The  phosphates,  sulphates,  and  carbonates  in  the  urine  inter- 
fere with"  the  application  of  the  method.  They  are  removed 
by  the  baryta  mixture,  composed  of 

2  volumes  of  a  cold  saturated  solution  of  barium  hydroxide 
(Ba(OH)2). 

1  volume  of  a  cold  saturated  solution  of  barium  nitrate 
(Ba(N03)2). 

Method :  40  c.c.  urine  are  mixed  with  20  c.c.  baryta  mix- 
ture, and  filtered  through  a  filter  that  has  not  been  previously 
moistened  with  water.  The  filtrate  is  neutralized  with  a  drop 
or  more  of  nitric  acid.  15  c.c.  of  the  filtrate  (representing 
10  c.c.  urine  and  5  c.c.  baryta  mixture)  are  transferred  by 
means  of  a  pipette  to  a  beaker,  and  the  mercuric  nitrate  solu- 
tion is  run  into  it  from  a  burette,  stirring  after  each  addition, 
until  a  permanent  milky  turbidity  is  produced  (action  on  the 
urea).  The  quantity  of  mercuric  nitrate  solution  added  up  to 
this  point  was  required  by  the  sodium  chloride. 

The  number  of  c.c.  mercuric  nitrate  solution  added  up  to 
this  point  is  noted  and  the  number  noted  multiplied  by  0.0418, 
will  represent  the  quantity  of  sodium  chloride  in  10  c.c.  of  the 
urine,  and  this,  multiplied  by  }0,  gives  the  percentage. 

The  addition  of  the  mercuric  nitrate  solution  is  continued, 
stirring  after  each  addition,  until  a  drop  of  the  liquid  in  the 
beaker  produces  a  slight  yellow  color  when  brought,  by  means 
of  a  glass  rod,  in  contact  with  the  indicator  (sodium  carbonate) 
on  a  porcelain  tablet. 

The  total  number  of  c.c.  of  mercuric  nitrate  solution  required 
for  the  sodium  chloride  and  urea  is  read  off.  From  this  number 
the  quantity  required  for  the  sodium  chloride  is  deducted  and 
the  remainder  will  be  the  quantity  required  for  the  urea. 

If  more  than  30  c.c.  of  mercuric  nitrate  solution  have  been 
required  for  the  urea  alone,  then  for  every  4  c.c.  required  over 
30  c.c.  add  0.1  c  c.  to  the  number  of  c.c.  of  mercuric  nitrate 
solution  required  for  the  urea  alone. 

If  less  than  30  c.c.  of  mercuric  nitrate  solution  have  been 
required  for  the  urea  alone,  then  for  every  4  c.c.  required  less 
than  30  c.c.  deduct  0.1  c.c.  from  the  number  of  c.c.  of  mercuric 
nitrate  solution  required. 


NOTES  ON  CHEMICAL  LECTURES.  75 

The  corrected  number  of  c.c.  mercuric  nitrate  solution  is 
multiplied  by  0.010,  and  the  result  will  represent  the  quantity 
of  urea  in  10  c.c.  of  the  urine,  and  this  result  multiplied  by  10, 
gives  the  percentage  of  urea  in  the  urine. 

Example  :  Suppose  a  total  quantity  of  36  c.c.  mercuric 
nitrate  solution  had  been  required, 

36  c.c. 

_2  c.c.  for  NaCl. 

34  c.c.  for  urea. 

30 

4  (once  4  over  30). 
Hence 

34.0  c.c.  +  0.1  =  34.1  c.c. 
341  X  0.010  =  0.341  grm. 
0.341  X  10  =  3.41  per  cent.  urea. 

These  corrections  are  necessary  to  make  the  results  corre- 
spond to  the  end  reaction  obtained  in  standardizing  the  mer- 
curic nitrate  solution,  in  which  there  were  just  two  volumes 
of  the  mercuric  nitrate  solution  employed  for  one  volume  of 
the  urea  solution. 

CORRECTIONS  FOR  VARYING  QUANTITIES  OF  UREA. 

a.  If  the  undiluted  urine  under  examination  contains  over 
3  per  cent,  of  urea,  then  on  mixing  it  with  the  baryta  fluid  in 
the  proportion  of  10  c.c.  of  the  urine  with  5  c.c.  of  the  baryta 
fluid,  the  resulting  mixture  will  contain  over  2  per  cent,  of  urea. 

Under  these  circumstances  15  c.c.,  or  say  one  volume,  of 
the  urine  mixture  will  require  over  30  c.c.,  or  two  volumes,  of 
the  mercuric  nitrate  solution  for  complete  precipitation  of  the 
urea. 

Consequently,  the  excess  of  the  mercuric  oxide  originally 
present  in  the  mercuric  nitrate  solution  for  the  purpose  of 
acting  upon  the  indicator  (sodium  carbonate)  will  be  under  a 
less  degree  of  dilution  than  was  present  when  the  mercuric 
nitrate  solution  was  standardized,  and  hence  a  portion  of  this 
excess  will  be  consumed  in  the  precipitation  of  the  urea,  there 
still  being  left  in  excess  a  quantity  of  mercuric  oxide  equal  to 
10 


76  NOTES  ON  CHEMICAL  LECTURES. 

that  originally  present  when  the  mercuric  nitrate  was  stand- 
ardized ;  namely,  3.466  milligrammes  in  each  c.c.  of  the  end 
mixture. 

The  quantity  of  the  excess  of  mercuric  oxide  thus  consumed 
by  urea  can  be  accurately  compensated  for  by  adding  to  the 
number  of  cubic  centimetres  of  mercuric  nitrate  solution  em- 
ployed 0.1  c.c.  for  every  4  c.c.  of  the  mercuric  nitrate  solution 
required  above  30  c.c. 

Thus  if  34  c.c.  of  the  mercuric  nitrate  solution  are  required, 
it  should  be  read  34.1  c.c.,  which  would  indicate  that  the  un- 
diluted urine  contained  3.41  per  cent,  of  urea. 

b.  Should  the  undiluted  urine  contain  less  than  3  per  cent, 
of  urea,  then  on  mixing  10  c.c.  of  the  urine  with  5  c.c.  of  the 
baryta  fluid,  the  resulting  mixture  will  contain  less  than  2  per 
cent,  of  urea,  and,  consequently,  15  c.c.  of  the  mixture  will 
require  less  than  30  c.c.  of  standard  mercuric  nitrate  solution 
for  the  complete  precipitation  of  the  urea. 

Under  these  conditions  the  original  excess  of  mercuric  oxide, 
in  the  mercuric  nitrate  solution  for  the  purpose  of  acting  upon 
the  indicator,  will  be  under  a  greater  degree  of  dilution  than 
existed  when  the  mercuric  nitrate  solution  was  standardized, 
and,  therefore,  a  portion  of  the  mercuric  oxide  intended  for  the 
precipitation  of  the  urea,  will  be  consumed  by  acting  on  the 
indicator.  Hence,  when  less  than  30  c.c.  of  the  mercuric 
nitrate  solution  are  required  for  a  mixture  of  10  c.c.  of  urine 
and  5  c.c.  of  baryta  fluid,  deduct  from  the  reading  0.1  c.c.  for 
every  4  c.c.  of  mercuric  nitrate  solution  required  less  than 
30  c.c.  Thus,  if  26  c.c.  of  mercuric  nitrate  solution  were 
required,  it  should  be  read  25.9  c.c.,  which  would  indicate  that 
the  undiluted  urine  contained  2.59  per  cent,  of  urea. 

In  other  words,  these  corrections  may  be  stated  as  follou's  : 
For  each  c.c.  of  mercuric  nitrate  solution  required  above  two 
volumes  of  the  mercuric  nitrate  solution  for  one  volume  of 
the  urine  mixture,  add  0.025  c.c.  to  the  reading ;  and  for  each 
c.c.  of  the  mercuric  nitrate  solution  required  less  than  two 
volumes  of  mercuric  nitrate  solution  for  one  volume  of  the 
urine  mixture,  deduct  0.025  c.c.  from  the  reading. 

Examples :  A. — 10  c.c.  of  2  per  cent,  urea  solution,  plus 
20  c.c.  of  the  HgO  solution.  Thus,  in  each  c.c.  of  the  HgO 


NOTES  ON  CHEMICAL  LECTURES.  77 

solution  there  are  5.2  milligrammes  of  HgO  in  excess  to  act 
on  the  indicator.  In  20  c.c.  there  are  5.2  X  20  =  104  milli- 
grammes excess  of  HgO  in  the  30  c.c.  of  end  mixture.  There- 
fore in  each  c.c.  of  the  30  c.c.  of  mixture  there  are  104  -=-  30  or 
3.46(3  milligrammes  of  HgO  in  excess  to  act  on  the  indicator. 

B. — 10  c.c.  of  urine  containing  3  per  cent,  of  urea,  plus  5  c.c. 
of  baryta  niixf2ire,  plus  30  c.c.  of  HgO  solution.  In  each  c.c. 
of  HgO  solution  there  are  5.2  milligrammes  excess  of  HgO. 
In  30  c.c.  there  are  30  X  5.2  milligrammes  =  156  milligrammes 
excess  in  45  c.c.  of  end  mixture.  Therefore  in  1  c.c.  there  are 
156  -*-  45  =  3.466  milligrammes. 

C. — 10  c.c.  of  urine  containing  4  per  cent,  of  urea,  plus  5  c.c* 
of  baryta  mixture,  plus  40  c.c.  of  HgO  solution.  In  40  c.c.  of 
HgO  solution  there  are  40  X  5.2  =  i08  milligrammes  excess 
of  HgO  in  55  c.c.  of  end  mixture.  Therefore  in  1  c.c.  there 
are  208  -4-  55  =  3.781.  But  adding  5  c.c.  of  H,O  to  the  mix- 
ture, there  are  208  milligrammes  of  HgO  excess  in  60  c.c. 
mixture,  and,  therefore,  in  1  c.c.  there  are  208  -=-  60  =  3.466. 

In  the  case  of  a  urine  containing  4  per  cent,  of  urea,  10  c.c. 
of  the  urine  would  contain  400  milligrammes  of  urea  and, 
with  the  dilution  of  5  c.c.  of  baryta  mixture,  should  require 
40  c.c.  of  standard  mercuric  nitrate  solution.  As  a  matter  of 
fact  the  action  on  the  indicator  will  occur  when  39.76  c.c.  of 
mercuric  nitrate  solution  have  been  added,  for  after  that  quan- 
tity has  been  added,  each  c.c.  of  the  end  mixture  will  contain 
3.460  milligrammes  of  HgO.  Each  c.c.  of  the  mercury  solu- 
tion contains  72  mgrms.  of  HgO  *  which  is  designed  to  com- 
bine with  10  mgrms.  urea,  therefore,  400  mgrms.  of  urea 
would  require  40  X  0.072  =  2.880  grms.  HgO.  In  the  39.76 
c.c.  mercury  solution  actually  required  there  are  39.76  X 
0.0772  HgO  =  3.069  grms.  HgO.  From  this  quantity  of 
HgO,  which  is  designed  for  both  urea  and  indicator,  must  be 
deducted  the  quantity  of  HgO  required  for  the  400  mgrms.  of 
urea,  namely,  2.880  grms.  Thus,  3.069  —  2.880  =  0.189472 
mgrms.,  which  is  the  quantity  of  HgO  distributed  in  the  end 
mixture  to  act  upon  the  indicator,  consequently  in  each  c.c.  of 
the  end  mixture  (composed  of  10  c.c.  urine  -f  5  c.c.  baryta 
mixture  -j-  39.76  c.c.  mercury  solution  —  54.76  c.c.)  there  are 

*  Oth«p  than  the  5.2  mgrms.  HgO  for  the  indicator. 


78  NOTES  ON  CHEMICAL  LECTURES. 

0.189472  -r-  54.76  =  0.00346  mgrms.  HgO  to  act  upon  the 
indicator.  39.76  c.c.  mercury  solution^  employed  —  30  c.c. 
mercury  solution  the  basis  for  which  no  correction  is  neces- 
sary, =  9.76  -=-  4  =  2.44  the  number  of  tenths  which  must  be 
added  to  the  number  39.76  to  make  it  correspond  to  the 
correct  number  of  cubic  centimetres, — namely  40.  Therefore, 
in  the  correction,  each  4  c.c.  of  mercury  solution  used  above 
30  c.c.  are  equivalent  to  one-tenth  of  a  cubic  centimetre  of  the 
standard  mercuric  nitrate  solution. 

D. — 10  c.c.  of  urine  containing  2  per  cent,  of  urea,  plus  5  c.c. 
of  baryta  mixture,  plus  20  c.c.  of  HgO  solution.  In  20  c.c.  of 
HgO  solution  there  are  5.2  X  20  or  104  milligrammes  of  HgO 
excess  in  35  c.c.  of  end  mixture.  Therefore  in  each  c.c.  there 
are  104  -=-  35  =  2.971.  But  10  c.c.  of  a  2  per  cent,  urea  solu- 
tion plus  5  c.c.  of  baryta  mixture  will  require  20.23  c.c.  of 
HgO.  In  20  c.c.  of  HgO  solution  there  are  20  X  5.2  =  104 
milligrammes  in  excess.  Each  c.c.  of  the  standard  solution  of 
HgO  contains  77.2  milligrammes  of  HgO,  therefore  0.23  c.c. 
will  contain  77.2  X  0.23  =  17.75  in  excess,  plus  104  =  121.75 
-4-  35.23  •=  3.466  mgrms. 

PHOSPHORIC  ACID. 

Phosphoric  acid  occurs  in  the  urine  partly  in  combination 
with  sodium,  potassium,  and  ammonium  (alkaline  phosphates), 
and  partly  with  calcium  and  magnesium  (earthy  phosphates). 

It  also  occurs  in  small  quantity  in  the  urine  as  glycerine 
phosphoric  acid  (C3H9PO6). 

/OH 

PO  —  OH  =  Glycerine  phosphoric  acid. 

\OC3H5(OH)2 

About  four-fifths  of  the  phosphoric  acid  in  the  urine  is  in 
combination  as  alkaline  phosphates,  and  one-fifth  as  earthy 
phosphates. 

Phosphoric  acid  in  the  urine  is  determined  in  terms  of  P2O5 
(phosphoric  anhydride). 

The  volumetric  method  for  the  quantitative  deter- 
mination of  phosphoric  acid  in  the  urine  depends  upon  the 


f 


: 


-f- 


NOTES  ON  CHEMICAL  LECTURES.  79 

principle  that  P2O5  in  the  presence  of  free  acetic  acid  and  an 
acetate  of  an  alkali,  on  the  application  of  heat,  is  precipitated 
by  uranium  acetate,  or  nitrate,  as  insoluble  (UrO3)2P2O5. 

It  is  always  necessary  to  standardize  the  uranium  solution 
with  a  standard  solution  of  P2O3. 

The  standard  solution  of  P2O5  is  prepared  so  that  it  shall 
contain  0.2  per  cent.  P2O5. 

1.  Preparation  of  standard  solution  of  P2O5:    Di-sodic 
hydrogen  phosphate  (Na2HPO4  +  12H2O)  is  selected  for  this 
purpose. 

Two  molecules  of  Na2HPO4  -j-  12H2O  contain  one  molecule 
of  P205. 

Na2HPO4  +  12H2Q  =  358  X  2  =  716 
PA  =  142 

Hence,  to  determine  the  quantity  of  Na2HPO4  -f-  12H2O 
necessary  to  prepare  1000  c.c.  solution,  so  that  it  shall  contain 
2  grm.  P2O5  (0.2  per  cent.), 

P20C.  2Na»HPO4  +  12H2O.  P2O5.  Na2HPO4  +  12H2O. 

142        :        716        ::         2       :       10.085  grm. 
or  to  prepare  only  250  c.c.  of  the  standard  Na2HPO4  +  12H2O 
solution, 

NajjHP04  +  12H,O. 

142    :    716     ::     0.5    :     2.521  grm. 

10.085  grm.  pure  non-effloresced  di-sodic  hydrogen  phos- 
phate are  dissolved  in  water  and  the  solution  diluted  to  1000 
c.c.,  or  to  prepare  only  250  c.c.  of  the  solution,  2.521  grm.  of 
the  phosphate  are  dissolved  in  water  and  diluted  to  250  c.c. 

P205. 

1000  c.c.  =  2.000  grm. 
100  c.c.  =  0.200     " 
50  c.c.  =  0.100     " 
1  c.c.  =  0.002     " 

2.  Preparation  of  uranium  acetate,  or  nitrate  solution ; 
The  precipitate  formed  when  uranium  acetate,  or  nitrate,  is 
added  to  a  solution  containing  P2O5  is  (UrO3)2P2O5, — /.  e.,  two 
molecules  of  UrO3  in  combination  with  one  molecule  of  P2O5. 

288. 

Twice  the  molecular  weight  of  UrO3  is  576 

142. 

Once  "  "  P2O5   "  142 


80  NOTES  ON  CHEMICAL  LECTURES. 

The  quantity  of  uranium  oxide  (UrO3)  required  to  prepare 
1000  c.c.  of  standard  solution  so  that  1  c.c.  shall"  equal  0.010 
P2O5  is  determined  : 

P2O5.       2UrO3.         PoO5.        UrO3. 

142  :  576  ::   10  :  40.56  grm.  =  to  10  grm.  P2O5 
The  quantity  of  uranium  acetate  (UrO3(C2H3O2)2  +  2H2O) 
or  of  the  nitrate  (UrO3N2O5  +  6H2O)  equivalent  to  40.56  grm. 
UrO3  is  determined  : 


Uran.  acetate.          UrOs.        Uran.  acetate. 

288    :    442    ::    40.56    :    62.24  grm. 

UrOs-    Uran.  nitrate.          UrOg.        Uran.  nitrate 

288    :    504    ::    40.56    :    70.98  grm. 

The  quantity  of  uranium  acetate  or  of  nitrate  necessary 
to  prepare  1000  c.c.  of  solution  may  also  be  calculated  by  one 
proportion  : 

P2O5.        2  Uran.  acetate.        P2O5.  Uran.  acetate.  fl  /°    W    /      "7  &4* 

142     :     884      ::      10     :     62.24  grm.^^  * 

PoO5.        2  Uran.  nitrate.          PoOs-  Uran.  nitrate. 

142     :     1008     ::      10     :      70.98  grm. 

Because  of  uranium  acetate  and  nitrate  being  contaminated 
with  oxides  of  uranium  the  respective  quantities,  as  indicated 
by  the  above  proportions,  are  dissolved  in  900  c.c.  water 
instead  of  1000  c.c. 

Ammonium  salts  in  the  urine  interfere  with  uranium  nitrate, 
therefore  uranium  acetate  is  preferred  in  the  preparation  of  the 
standard  solution. 

62.24  grm.  uranium  acetate  or  70.98  grm.  uranium  nitrate 
are  boiled  with  about  850  c.c.  water,  the  liquid  allowed  to  cool, 
the  insoluble  oxides  of  uranium  are  removed  by  filtration  and 
the  solution  diluted  to  900  c.c. 

3.  Preparation  of  the  solution  containing  an  acetate  of 
an  alkali  and  free  acetic  acid  :  50  grm.  sodium  acetate  are 
dissolved  in  450  c.c.  water,  and  acetic  acid  is  added  until  the 
volume  reaches  500  c.c. 

4.  The  indicator  is  a  solution  of  potassium  ferrocyanide  of 
about  ten  per  cent,  strength.     With  a  soluble  uranium  salt  it 
produces  a  chocolate  color  (due  to  formation  of  uranium  ferro- 
cyanide). 


V 


NOTES  ON  CHEMICAL  LECTURES.  81 

Standardizing  the  uranium  acetate  solution :  To  stand- 
ardize the  uranium  acetate  solution,  50  c.c.  of  the  standard 
phosphoric  acid  solution  (containing  0.100  grm.  P2O5)  are 
placed  in  a  beaker,  5  c.c.  of  the  acetate  of  an  alkali  solution 
are  added  and  the  liquid  is  heated  to  the  simmering-point. 
The  uranium  acetate  solution  (about  one-half  c.c.  at  a  time)  is 
run  into  it  from  a  burette,  stirring  after  each  addition,  until  a 
drop  of  the  liquid  in  the  beaker  produces  a  slight  chocolate 
color  when  brought,  by  means  of  a  glass  rod,  in  contact  with 
the  potassium  ferrocyanide  solution  on  a  porcelain  tablet. 

The  number  of  cubic  centimetres  of  uranium  acetate  solu- 
tion required  to  effect  this  result  is  noted. 

Example :  Suppose  8  c.c.  of  uranium  solution  were  re- 
quired. The  solution  is  too  strong  and  must  be  diluted.  For 
every  8  c.c.  of  the  uranium  solution  (of  the  900  c.c.)  remaining, 
a  volume  of  water  equal  to  the  difference  between  8  and  10, 
or  2  c.c.  must  be  added. 

900  c.c.    original  volume  of  solution. 
8  c.c.    volume  used. 

8)892  c.c.    volume  remaining. 

111.5  X  2  =  223  c.c.  water  to  be  added  to  the  892  c.c. 
uranium  solution. 

P205. 

10  c.c.  will  now  equal  0.100  grm. 
1  c.c.    "      "         "       0.010     " 

Method :  50  c.c.  urine  are  placed  in  a  beaker,  5  c.c.  acetate 
of  an  alkali  solution  are  added  and  the  liquid  is  heated  to  the 
simmering-point.  The  uranium  acetate  solution  (about  one- 
half  c.c.  or  less,  at  a  time)  is  slowly  run  from  a  burette  into  the 
liquid  in  the  beaker,  stirring  after  each  addition,  until  a  drop 
of  the  liquid  in  the  beaker  produces  a  slight  chocolate  color 
when  brought,  by  means  of  a  glass  rod,  in  contact  with  potas- 
sium ferrocyanide  solution  on  a  porcelain  tablet. 

The  first  titration  (adding  about  0.5  c.c.  at  a  time)  usually 
gives  only  approximate  results,  unless  performed  with  great 
care.  A  second  titration  should  be  made,  and  the  uranium 
solution  slowly  run  in  until  within  0.5  c.c.  of  the  quantity 
required  in  the  first  titration.  The  uranium  solution  is  now 
added,  0.1  c.c.  at  a  time,  and  continued,  testing  with  the  indicator 


82  NOTES  ON  CHEMICAL  LECTURES. 

after  each  addition,  until  a  slight  chocolate  color  is  obtained  in 
the  potassium  ferrocyanide  solution  on  the  porcelain  tablet. 

The  number  of  cubic  centimetres  of  uranium  acetate  solution 
required  is  read  off  the  burette  and  this  number  is  multiplied 
-by  0.010,  and  the  result  will  represent  the  quantity  of  P2O5  in 
50  c.c.  urine.  This  result  multiplied  by  2  gives  the  percentage 
of  P2O5  in  the  urine. 

Example  :  Suppose  8.6  c.c.  uranium  solution  were  required. 
Then 

8.6  X  0.010  =  0.086  X  2  =  0.172  per  cent.  P2O5  (total). 

QUANTITATIVE  DETERMINATION  OF  THE  EARTHY 
PHOSPHATES  IN  URINE. 

To  200  c.c.  urine  excess  of  ammonium  hydroxide  (NH4OH) 
(about  10  c.c.  ordinary  strength  NH4OH),  is  added  and  the 
liquid  allowed  to  stand  twelve  hours.  The  precipitated  earthy 
phosphates  (phosphates  of  calcium  and  magnesium)  are  col- 
lected on  a  filter  and  washed  several  times  with  small  quanti- 
ties of  water  containing  a  few  drops  of  NH4OH.  A  beaker 
with  a  50  c.c.  mark  on  it  is  now  placed  under  the  funnel.  The 
filter,  while  in  the  funnel,  is  pierced  with  a  glass  rod,  and  the 
precipitate  treated  drop  by  drop  with  about  3  or  4  c.c.  acetic 
acid.  This  is  for  the  purpose  of  dissolving  the  earthy  phos- 
phates. The  remainder  of  the  precipitate  on  the  filter  is 
washed  with  water  into  the  beaker  below  until  50  c.c.  liquid 
are  collected  in  the  beaker.  Any  insoluble  matter  in  the  liquid 
in  the  beaker  is  mostly  mucous  from  the  urine.  No  attention 
need  be  paid  to  this. 

5  c.c.  of  acetate  of  alkali  solution  are  added  and  the  liquid 
is  heated  to  the  simmering-point. 

The  uranium  acetate  solution  (less  than  one-half  c.c.  at  a 
time)  is  slowly  run  from  a  burette  into  the  liquid  in  the  beaker, 
stirring  after  each  addition,  until  a  drop  of  the  liquid  in  the 
beaker  when  brought,  by  means  of  a  glass  rod,  in  contact  with 
potassium  ferrocyanide  solution  on  a  porcelain  tablet,  produces 
a  slight  chocolate  color. 

The  number  of  cubic  centimetres  of  uranium  acetate  solution 
required  is  read  off  the  burette  and  this  number  is  multiplied 


NOTES  ON  CHEMICAL  LECTURES.  83 

by  0.010,  the  result  is  divided  by  2  (because  200  c.c.  of  urine 
had  been  originally  employed).  The  final  result  will  represent 
the  percentage  of  P2O5  in  combination  with  the  alkaline  earths 
in  the  urine. 

Example  :  Suppose  5.4  c.c.  uranium  acetate  solution  were 
required. 

5.4  X  0.010  =  0.054  -5-  2  =  0.027  per  cent,  of  P2O5 

The  percentage  of  earthy  phosphates  is  deducted  from  the 
percentage  of  total  phosphates  (alkaline  +  earthy),  and  the 
remainder  is  the  percentage  of  P2O5  in  combination  with  the 
alkalies. 

Suppose  the  percentage  of  total        P2O3  =  0.172  per  cent. 

earthy       "     =0.027 

alkaline     "     =0.145 
Phosphoric  acid  often  occurs  in   urinary  sediments  as  triple 

phosphate  (magnesium  ammonium  phosphate,  MgNH4PO4). 
Phosphoric  acid  may  occur  in  combination  in  the  form  of 

urinary  calculi.     Phosphatic  calculi  do  not  occur  as  frequently 

as  uric  acid  calculi. 

PHOSPHATIC  CALCULI  MAY  OCCUR  IN  THREE 
FORMS. 

1.  Composed  of  calcium  phosphate  :  Three  varieties, — 
acid,  neutral,  and  basic. 

a.  CaH4(P04)2 

b.  CaHPO4 
ft   Ca3(P04)2 

All  are  soluble  in  nitric  acid  ;  when  their  solution  is  neutral- 
ized with  NH4OH  they  are  reprecipitated. 
Heat  does  not  affect  them. 

2.  Composed    of    magnesium    ammonium    phosphate 
(MgNH4PO4),  (triple  phosphate)  the  most  common  form. 

Soluble  in  hydrochloric  acid.  When  the  hydrochloric  acid 
solution  is  neutralized  with  NH4OH,  crystalline  triple  phos- 
phate appears.  When  heated,  ammoniacal  gas  is  evolved. 

3.  Fusible   phosphates,  usually  composed  of  i   and   2 
(above).     Contain  more  or  less  organic  matter. 

11 


84  NOTES  ON  CHEMICAL  LECTURES. 

URIC  ACID,  (Lithic  acid).     C.H4N4O3. 

Molecular  weight,  168. 

A  dibasic  acid, — /.  e.,  contains  two  replaceable  atoms  of 
hydrogen,  H2C5H2N4O3- 

Found  in  urine  chiefly  as  sodium  acid  urate,  NaHC-H2N4O3. 

Present  from  0.2  part  to  1.0  part  in  1000  parts  urine. 

Average  percentage  in  urine  0.05  per  cent. 

Recognized  as  a  distinct  compound  by  Scheele  in  177<). 
Studied  more  fully  by  Liebig  in  1838.  Was  prepared  syn- 
thetically in  1882. 

Formerly  called  lithic  acid. 

It  is  contained  in  the  solid  excrement  of  birds  and  serpents, 
from  which  source  it  is  most  readily  obtained  by  treating  the 
excrement  with  a  5  per  cent,  solution  of  NaOH,  filtering,  and 
adding  HC1  to  the  filtrate.  The  uric  acid  is  precipitated  in  an 
amorphous  state  or,  on  standing,  may  separate  in  crystalline 
form. 

It  may  be  deposited  in  the  joints,  as  in  the  uric  acid  diathesis 
(gout). 

To  obtain  pure  and  colorless  crystals  the  acid  obtained  from 
about  200  c.c.  of  urine  is  dissolved  in  about  75  c.c.  water  to 
which  about  1  c.c.  of  a  10  per  cent,  solution  of  NaOH  has 
been  added.  The  solution  is  slightly  acidulated  with  HC1, 
and  allowed  to  stand  twenty-four  hours  in  a  cool  place.  Uric 
acid  will  separate.  If  the  crystals  are  not  colorless,  they  are 
collected  on  a  filter,  redissolved  in  water  with  the  aid  of  NaOH, 
and  HC1  added  as  before.  The  operation  is  repeated,  if  neces- 
sary, until  colorless  crystals  are  obtained. 

Uric  acid  crystallizes  in  many  forms,  most  often  in  wedge- 
shaped  crystals. 

It  is  soluble  in  15,000  parts  of  cold  and  2000  parts  of  hot 
water.  Insoluble  in  alcohol  and  ether.  Soluble  in  an  alkaline 
solution  and  in  sulphuric  acid.  Insoluble  in  hydrochloric 
acid. 

When  burned,  an  odor  similar  to  burnt  feathers  is  pro- 
duced. 

It  is  dibasic ;  forms  neutral  and  acid  salts. 


NOTES  ON  CHEMICAL  LECTURES.  85 

Neutral  salts  :  a.  K2C5H2N4O3,  potassium  urate,  soluble  in 
44  parts  of  cold  water. 

~&  Na2C5H2N4O3,  sodium  urate,  less  soluble  than  the  corre- 
sponding neutral  potassium  salt. 

c.  The  neutral  ammonium  salt  is  unknown. 

Acid  salts  ;  a.  KHC5H2N4O3,,  acid  potassium  urate,  soluble 
in  SpOparts  of  water. 

b~.  NaTlC5H2N4O3,  acid  sodium  urate,  less  soluble  than  the 
corresponding  potassium  salt. 

c.  NH4HC5H2N4O3,  acid  ammonium  urate,  soluble  in  1800, 
parts  of  water. 

Uric  acid  treated  with  cold  strong  nitric  acid  (specific 
gravity  1.41)  is  oxidized,  with  the  formation  of  alloxan 
(C4H2N2O4).  Effervescence  occurs,  and  urea  is  produced  at 
the  same  time. 

C5H4N403  +  H20  +  O  =  C4H2N204  +/6o(NH2) 

Uric  acid.  Alloxan.  \ 

s 

Uric  acid  treated  with  hot  dilute  nitric  acid  is  oxidized,  with 
the  formation  of  alloxantin  (C8H4N4O7). 


QUALITATIVE  TESTS  FOR  URIC  ACID. 

1.  Murexide  test:    The    solid    uric   acid,  or   its    solution 
evaporated  to  dryness,  is  placed  in  a  small  porcelain  dish  and 
the  uric  acid  covered  with  strong  nitric  acid.      The  mixture  is 
evaporated  to  dryness  on  a  water-bath,  the  dish  allowed  to 
cool  and  the  residue  is  moistened  with   a  drop  of  very  dilute 
ammonium   hydroxide.      A   beautiful    red   color  will  appear, 
due   to   the  formation  of  murexide   (ammonium  purpurate), 
C8H8N606  =  (NH4C8H4N506). 

2.  SchifFs  test  :  The  uric  acid  is  dissolved  in  a  solution  of 
sodium  carbonate,  and  a  drop  of  the  solution  is  brought  in 
contact  with  filter-paper  which  has  been  previously  saturated 
with  a  solution  of  argentic  nitrate.     Spots  of  reduced  silver  of 
a  yellowish-brown  or  deep-black  color,  depending  upon  the 
quantity  of  uric  acid  in  the  solution,  will  appear  on  the  paper. 

Hippuric  acid  (C9H9NO3)  is  contained  in  very  small  quantity 
in  human  urine. 


86  NOTES  ON  CHEMICAL  LECTURES. 

Benzole  acid  (C7H6O2)  when  taken  into  the  human  organism 
is  converted  into  hippuric  acid  through  the  agency  of  glycocol 
(C2H5NO2),  a  substance  formed  in  the  liver,  thus : 

C7H6O2   +   C2H5NO2  =   C9H9NO3   +    H2O 

Benzoic  acid.  Glycocol.  Hippuric  acid. 

Quinic  acid  (C7H12O6),  one  of  the  acids  contained  in  cinchona 
bark,  and  also  in  coffee-beans,  is  eliminated  as  hippuric  acid. 
Hippuric  acid  appears  in  the  urine  after  eating  cranberries. 

QUANTITATIVE   DETERMINATION   OF  URIC  ACID  BY  MEANS 

OF  HCI. 

1.  Heintz's  method:  If  albumen  be  present  it  must  be 
removed  by  coagulation  by  heat  and  filtration.  To  200  c.c. 
urine  (if  not  clear,  filter,)  5  or  10  c.c.  HCI  are  added  and  the 
liquid  is  allowed  to  stand  about  twenty-four  hours.  Uric  acid 
separates  in  crystalline  form.  Some  of  the  crystals  float  on 
the  surface  of  the  liquid.  The  crystals  separated  in  this 
manner  are  brownish-red  in  color  owing  to  urine  coloring 
matter  which  they  have  taken  up  in  the  process  of  crystalliza- 
tion. 

The  crystals  are  collected  on  a  washed,  or  on  an  equipoised, 
or  a  weighed  washed  filter.  The  filtrate  is  used  to  wash  the 
crystals  out  of  the  beaker.  The  crystals  are  washed  with 
small  portions  of  water  (5  c.c.)  at  a  time  until  the  last  portions 
of  the  filtrate  coming  from  the  funnel  are  free  from  hydro- 
chloric acid  (test  with  AgNO3  solution). 

The  two  equipoised  filters  are  separated,  the  crystals  allowed 
to  dry  on  the  filter,  and  the  two  filters  are  weighed. 

The  weight  obtained  is  the  quantity  of  uric  acid  in  200  c.c. 
urine.  This  weight  divided  by  2  furnishes  the  percentage  of 
uric  acid  in  the  urine. 

If  over  30  c.c.  of  water  are  required  in  the  washing  of  the 
crystals,  then  for  every  cubic  centimetre  of  water  employed 
over  30  c.c.  0.000045  grm.  must  be  added  to  the  weight  of 
uric  acid  obtained.  (1  c.c.  water  applied  in  this  manner  dis- 
solves 0.000045  grm.  uric  acid). 

No  correction  is  necessary  when  only  30  c.c.  are  required 
in  the  washing. 


NOTES  ON  CHEMICAL  LECTURES.  87 

The  uric  acid  in  crystallizing  takes  up  coloring-matter  from 
the  urine,  but  the  amount  of  uric  acid  dissolved  by  the  30  c.c. 
water  used  in  washing  is  just  sufficient  to  compensate  for  the 
increase  of  weight  due  to  the  coloring-matter  taken  up. 

2.  xSalkowski-Ludwig  method :  Depends  upon  the  prin- 
ciple that  when  an  ammoniacal  solution  of  argentic  nitrate  is 
added  tox-^  solution  of  uric  acid,  to  which  an  ammoniacal 
mixture  of  magnesium  sulphate  and  ammonium  chloride  has 
been    previously    added,   the    uric    acid    is    precipitated    as    a 
magnesio-silver  salt.     This  is  collected  on  a  filter,  washed, 
and  decomposed  by  means  of  sodium  or  potassium  sulphide, 
whereupon  the  uric  acid  passes  into  solution  as  sodium  or 
potassium  urate.     On  the  addition  of  an  excess  of  hydrochloric 
acid  to  this   solution  the   urate  is  broken  up  and   uric   acid 
separates.     The  uric  acid  is  collected  on  a  previously  weighed 
or  an  equipoised  filter  and  weighed. 

3.  Haycraft's  method :  Depends  upon  the  principle  that 
when  uric  acid  is  precipitated  by  an  ammoniacal  solution  of 
argentic  nitrate,  in  the  presence  of  an  ammoniacal  mixture  of 
magnesium  sulphate  and  ammonium  chloride,  the  precipitate 
is  considered  to  contain  one  atom  of  silver  to  each  molecule 
of  uric  acid.     The  precipitate  is  collected  on  a  filter  and  dis- 
solved in  nitric  acid  of  about  1.12  to  1.18  specific  gravity,  in 
which  solution  the  uric  acid  is  determined  indirectly  by  deter- 
mining the  amount  of  silver  by  means  of  a  one-fiftieth  normal 
solution  of  potassium  sulphocyanate. 

Other  methods  for  the  quantitative  determination  of  uric  acid 
are  those  of  Fokker,  Camerer,  and  Czapek. 

CREATININE.     C4H7N3O. 

Molecular  weight,  113. 

First  recognized  in  1844.     Isolated  by  Liebig  in  1847. 

Occurs  in  the  urine  of  man  (0.06  per  cent.),  horse,  cow, 
sheep,  and  dog. 

A  substance  supposed  to  be  creatinine  was  found  in  muscle, 
but  was  afterwards  shown  to  be  creatine  (C4H9N3O2). 

Creatinine  crystallizes  in  colorless  prisms.  Soluble  in  12 
parts  of  water  and  in  100  parts  of  alcohol. 


88  NOTES  ON  CHEMICAL  LECTURES. 

Its  solution  is  strongly  alkaline  and  will  change  red  litmus 
to  blue,  and  will  change  turmeric  paper  brown.  It  has  a 
caustic  taste,  somewhat  like  dilute  ammonium  hydroxide.  It 

L&-4f4Ls\s*s^* 

is  the  strongest  of  all  bases  of  animal  origin. 

It  unites  with  acidsyXvithout  displacing  the  hydrogen  in  the 
acid,  to  form  salts,  as 

C4H-N3O  HC1  (creatinine  hydrochloride). 
It  combines  with  one  molecule  of  water  to  form  creatine : 
C4H7N3O  +  H2O  =  C4H9N3O2 

Creatinine.  Creatine. 

It  combines  with  zinc  chloride  to  form  creatinine  zinc 
chloride,  (C4H7N3O)2ZnCl2,  which  contains  62.432  per  cent,  of 
creatinine. 

QUALITATIVE  TESTS  FOR  CREATININE. 

1 .  Picric  acid  test :  A  solution  of  creatinine  treated  with 
a  few  drops  of  sodium  hydroxide  and  a  little  picric  acid  and 
then  warmed  is  colored  claret-red. 

2.  Weyl's  test ;  A  dilute  creatinine  solution  treated  with  a 
few  drops  of  very  dilute  sodium  nitroprusside  solution,  and 
then  with  a  dilute  solution  of  sodium  hydroxide,  added  drop 
by  drop,  becomes  ruby-red  in  color,  changing  in  a  few  moments 
to  an  intense  straw  color,  which  in  turn  becomes  green  when 
warmed  with  acetic  acid. 

Creatinine  reduces  Fehling's  solution  changing  the  blue 
liquid  to  yellow.  The  cuprous  oxide  does  not  separate,  but 
remains  in  solution. 

QUANTITATIVE  DETERMINATION  OF  CREATININE  IN  URINE. 

300  c.c.  urine  are  treated  with  milk  of  lime  until  slightly 
alkaline,  and  a  solution  of  calcium  chloride  is  added  as  long 
as  a  precipitate  forms  (may  require  5  to  8  c.c.  of  5  per  cent. 
CaCl2  solution).  The  liquid  is  filtered  and  the  filtrate  is 
evaporated  to  syrup-like  consistence  (to  about  20  c.c.)  on  a 
water-bath  and,  while  warm,  about  50  c.c.  alcohol  (95  per  cent.) 
are  added. 

The  liquid  is  stirred  with  a  glass  rod  until  a  precipitate  is 
formed.  (The  precipitate  may  form  only  after  long  stirring). 


NOTES  ON  CHEMICAL  LETCURES.  89 

The  precipitate  is  collected  on  a  filter  and  the  dish  and  the 
filter  are  washed  with  about  10  c.c.  alcohol  (in  2  or  3  portions), 
collecting  the  wash-alcohol  with  the  filtrate.  (The  precipitate 
may  be  thrown  away.)  The  beaker  containing  the  filtrate  is 
covered  and  allowed  to  stand  twenty-four  hours  in  a  cool 
place. 

A  precipitate  separating  after  the  liquid  has  stood  about 
twenty-four  hours,  is  collected  on  a  small  filter  and  washed 
with  about  10  c.c.  of  alcohol  (in  2  or  3  portions),  and  the 
washings  collected  with  the  filtrate. 

The  filtrate  is  concentrated  by  evaporation  to  about  60  c.c., 
and,  when  cold,  1  c.c.  of  acid  free  zinc  chloride  solution  of 
about  1.2  specific  gravity  is  added. 

The  liquid  is  stirred  with  a  glass  rod  until  a  precipitate 
(cloudiness)  begins  to  appear.  (The  precipitate  may  appear 
only  after  long  stirring.)  The  beaker  is  then  covered  and 
allowed  to  stand  two  or  three  days  in  a  cool  place  to  permit 
crystallization  to  occur.  Creatinine  zinc  chloride  separates  in 
crystalline  tufts  or  rosettes. 

The  precipitate  of  creatinine  zinc  chloride  is  collected  on  an 
equipoised  filter  (using  the  filtrate,  if  necessary,  to  transfer  the 
precipitate  from  the  beaker). 

The  precipitate  on  the  filter  is  washed  with  alcohol  (2  or 
3  c.c.  at  a  time)  until  the  filtrate  is  colorless  and  free  from 
chlorine  (test  last  portions  of  the  filtrate  coming  from  the 
funnel  with  AgNO3).  The  precipitate  is  dried  on  the  filter  at 
a  temperature  of  100°  C.  and,  when  dry,  weighed. 

Every  100  parts  (C4H7N3O)2ZnCl2  contain  62.432  parts 
creatinine. 

Then, 

100  :  62.432   ::  weight  of  precipitate  :  x  =  quantity  of 
creatinine  in  the  300  c.c.  urine  employed. 

To  obtain  the  percentage  of  creatinine  divide  the  result  by 
3,  because  300  c.c.  of  urine  were  originally  employed. 

The  creatinine  may  be  obtained  from  the  creatinine  zinc 
chloride  by  dissolving  the  latter  in  hot  water  and  boiling  it 
from  one-quarter  to  one-half  hour  with  freshly  precipitated, 
well-washed  plumbic  hydroxide  (prepared  by  precipitating 


90  NOTES  ON  CHEMICAL  LECTURES. 

plumbic  acetate  with  ammonium  hydroxide)  or  with  basic 
plumbic  carbonate  (prepared  by  precipitating  plumbic  acetate 
with  sodium  carbonate).  When  cool,  the  liquid  is  filtered  and 
the  filtrate  decolorized  by  warming  it  with  animal  charcoal. 
The  filtrate  from  the  animal  charcoal  is  evaporated  to  dryness 
on  a  water-bath.  The  residue,  in  addition  to  creatinine,  con- 
tains creatine,  which  has  resulted  from  the  breaking  up  of 
some  of  the  creatinine  in  the  boiling  with  plumbic  hydroxide. 
To  separate  them  the  residue  is  treated  with  cold  concentrated 
alcohol,  which  dissolves  the  creatinine  and  leaves  the  creatine 
undissolved.  The  liquid  is  filtered  and  the  filtrate  is  allowed 
to  evaporate  at  ordinary  temperature.  Creatinine  will  separate 
from  the  liquid  in  crystalline  form. 

SUGARS. 

1.  Glucose  group  :  C6H12O6. 

Dextrose  (polarizes  light  to  the  right). 
Lactose. 
Grape  sugar. 

Laevulose  (polarizes  light  to  the  left). 
Fruit  sugar. 
Mannitose. 
Inosite. 
Sorbine. 
Etc. 

Glucoses,  by  the  action   of  a  ferment,  are  converted  into 
alcohol  and  carbon  dioxide. 

C6H12O6  =  2C2H5OH  +  2CO2 

Diastase,  a  ferment,  converts  starch  (C6H10O5)  into  dextrose 
(C6H12O6). 

Starch  warmed  with  dilute  sulphuric  acid  or  dilute  hydro- 
chloric acid  is  converted  into  dextrose  (glucose). 

3C6H1005  +  3H20  +  (H2S04)X  =  3C6H12O6  +  (H2SO4)X 

Dextrine  may  be  formed  at  the  same  time. 
3C6H1005  +  H20 +(H2S04)X  =  C6H120G  +  2C6H10O5  +  (H2SO4)X 

Dextrine. 

Dextrine  is  a  gummy  substance. 


NOTES  ON  CHEMICAL  LECTURES.  91 

2.  Saccharose  group:  C^H^On. 

Saccharose  (cane  sugar). 
Milk  sugar. 
Maltose. 
Etc. 

Cane  sugar,  Cl2H.aOllt  warmed  with  dilute  sulphuric  acid  is 
converted  into  glucose  and  laevulose,  the  mixture  of  the  two 
latter  is  termed  fruit  sugar. 

CMHaOu  +  H20  +  (H2S04)X  =  C6H12Oti  +  C6H12O6 

Glucose.  Laevulose. 

3.  Amylose  group  :  C6H10O;;. 

Starch. 
Dextrine. 
Cellulose. 
Arabinose. 
Etc. 

According  to  some  investigators,  the  formula  for  starch, 
instead  of  C6H10O5,  should  be  3C6H10O5  =  C^H^O^. 

Other  investigators  suggest  as  the  most  probable  formula 

4C6H10O5  =  C^H^OjjQ. 

Starch  is  not  determined  directly,  but  is  converted  into 
dextrose  (glucose)  by  being  warmed  with  dilute  sulphuric  acid 
or  dilute  hydrochloric  acid.  The  quantity  of  starch  is  calcu- 
lated from  the  quantity  of  dextrose  (glucose)  produced. 

ABNORMAL  CONSTITUENTS  OF  URINE. 

The  substances  occurring  in  the  urine  only  pathologically, 
or  only  very  seldom  in  soluble  form,  which  need  be  considered 
are  as  follows : 

Albumin  ;  globulin  ;  hemialbumose  ;  peptone  ;  mucin  ;  glu- 
cose ;  milk  sugar  ;  inosite  ;  dextrin  ;  bile  acids  ;  bile  coloring- 
matters  ;  blood  coloring-matter ;  urorubrohaematin  and  uroru- 
brofuscin  ;  melanin  ;  leucin  ;  t^rosin  ;  allantoin  ;  fat,  lecithin, 
and  cholesterin  ;  acetone  and  alcohol ;  Baumstark's  substance, 
C3H8N2O8 ;  urocaninic  acid  ;  hydrogen  sulphide  ;  diacetic  acid  ; 
homogentisic  acid  C8H8O4. 

12 


92  NOTES  ON  CHEMICAL  LECTURES. 

The  abnormal  constituents  of  the  urine  occurring  most 
frequently,  and  of  the  greatest  importance  to  the  physician, 
are  glucose  and  albumin. 

DIABETIC  URINE. 

Urine  containing  glucose  is  diabetic  urine. 

Synonyms  of  glucose :  dextrose,  grape  sugar,  diabetic 
sugar. 

Glucose  is  an  abnormal  constituent  of  urine. 

It  is  not  contained  in  normal  urine,  although  Pavy  claims 
that  it  is  present  in  minute  quantity  in  all  urine. 

Diabetic  urine  is  generally  paler  in  color  than  normal  urine 
and  has  a  sweet  taste. 

The  quantity  of  urine  voided  in  diabetes  mellitus  is  usually 
greater  than  in  health,  and  the  urinous  odor  of  normal  urine 
is  generally  absent. 

Its  specific  gravity,  as  a  rule,  is  higher  than  that  of  normal 
urine  (1030-1050,  and  even  1060). 

Glucose  may  be  present,  varying  from  a  trace  up  to  10—12 
per  cent.,  and  even  14  per  cent. 

When  diabetic  urine  is  exposed  to  the  air  for  a  time,  at  not 
too  low  temperature,  the  surface  often  becomes  covered  with 
a  scum  or  mould  (fungus),  due  to  the  multiplication  of  cells 
of  the  torula  cerevisiae,  originating  from  cells  derived  from 
the  air. 

A  scum  may  also  form  on  urine  not  containing  glucose,  but 
the  scum  in  such  case  is  not  due  to  the  torula  cerevisiae. 


QUALITATIVE  TESTS  FOR  GLUCOSE  IN  URINE. 

1.  Moore's  test :  To  the  urine  contained  in  a  test-tube 
about  one-fourth  its  volume  of  sodium  or  potassium  hydroxide 
solution  (about  10  per  cent,  strength)  is  added  and  the  liquid 
is  boiled.  If  glucose  be  present  the  liquid  will  become  brown 
or  black  in  color,  depending  upon  the  quantity  of  glucose. 

Delicacy  of  the  test,  0.3  per  cent,  glucose. 

The  test  is  unreliable,  because  normal  constituents  of  the 
urine,  particularly  mucin,  may  give  a  similar  coloration. 


NOTES  ON  CHEMICAL  LECTURES.  93 

2.  Johnson's  picric  acid  test ;  Picric  acid  (carbazotic  acid, 
trinitrophenol),  QH^NO^OH,  is  a  derivative  of  carbolic  acid 
(phenol),  C6H5OH.  " 

A  few  drops  of  a  saturated  aqueous  solution  of  picric  acid 
and  sufficient  sodium  hydroxide  (NaOH),  or  KOH  solution, 
to  render  the  urine  alkaline  are  added  to  the  urine  and  the 
liquid  is  warmed. 

If  glucose  be  present  the  liquid  will  become  claret-rgjdtjn  color, 
owing  to  the  production  of  picramic  acid  (C6H2(NO2)2NH2OH), 
(resulting  from  the  replacement  of  one  of  the  NO2  radicals  in 
picric  acid  by  the  NH2  radical,)  which  enters  into  combination 
with  the  alkali  present  to  form  a  salt, — a  picraminate  of  the 
alkali. 

Delicacy  of  the  test,  0.01  per  cent,  glucose. 

This  test  is  unreliable,  because  creatinine,  a  normal  con- 
stituent of  the  urine,  responds  in  a  similar  manner, — /.  e.,  gives 
a  claret-red  color. 

3.  Boettcher's  test    (bismuth  test) :    To  the   urine  about 
one^fourth  its  volume  of  sodium  or  potassium  hydroxide  solu- 
tion is  added.     A  portion  of  bismuth  oxynitrate  (subnitrate) 
about  the  size  of  a  mustard-seed  is  then  added  and  the  liquid 
is  boiled. 

If  glucose  be  present  the  bismuth  oxynitrate  will  be  reduced 
to  metallic  bismuth,  coloring  the  liquid  first  gray  and  then 
black,  or  the  reduced  metallic  bismuth  may  settle  in  the  bottom 
of  the  tube. 

Delicacy  of  the  test,  0.4  per  cent,  glucose. 

Albumin  must  be  removed  before  employing  this  test. 

Albumin  interferes  with  this  test  by  producing  a  similar 
change  of  color,  due  to  the  formation  of  black  bismuth  sul- 

o 

phide  (Bi2S3).  The  albumin  undergoes  decomposition  when 
heated  with  the  caustic  alkali,  forming  sodium  sulphide  (Na2S) 
(the  sulphur  being  derived  from  the  albumin),  which  acts  on 
the  bismuth  compound  to  form  bismuth  sulphide. 

4.  The  fermentation  test ;   Depends  upon  the  breaking  up 
of  glucose  into  alcohol  and  carbon  dioxide  by  the  action  of  a 
ferment, — /.  e.,  yeast. 

CGH12O6  =  2C2H5OH  +  2CO2 


94  NOTES  ON  CHEMICAL  LECTURES. 

A  test-tube  is  filled  with  the  urine,  and  a  drop  or  two  of 
brewer's  yeast  or  a  piece  of  compressed  yeast  about  the  size 
of  a  pea  is  added.  The  tube  is  inverted  over  some  of  the 
same  urine  contained  in  a  dish,  and  stood  aside  for  six  or  eight 
hours  in  a  place  where  the  temperature  is  between  70°  and 
100°  F. 

If  sugar  be  present  it  will  undergo  fermentation  with  the 
evolution  of  carbon  dioxide,  which  will  collect  in  the  upper 
part  of  the  inverted  tube. 

To  prove  that  the  gas  in  the  tube  is  carbon  dioxide,  a  piece 
of  sodium  hydroxide  is  inserted  in  the  tube,  the  opening  of 
the  tube  is  closed  with  the  thumb,  and  the  tube  agitated.  The 
carbon  dioxide  will  be  absorbed  by  the  sodium  hydroxide, 
forming  sodium  carbonate. 

As  yeast  itself  may  give  off  gas,  a  control  experiment  may 
be  performed  by  testing  the  yeast  in  the  same  manner,  but 
employing  water  in  the  test-tube  in  the  place  of  urine. 

Delicacy  of  the  test,  0.4  per  cent,  glucose. 

The  quantity  of  carbon  dioxide  evolved  from  0.4  per  cent,  of 
glucose  is  just  sufficient,  at  ordinary  temperature,  to  saturate 
the  water  in  which  it  is  contained  and,  therefore,  will  not  appear 
as  gas  in  the  upper  part  of  the  tube,  hence  the  delicacy  of  the 
test,  under  ordinary  conditions,  is  0.4  per  cent,  of  glucose. 

5.  Trommer's  test :  Depends  upon  the  reduction  of  cupric 
oxide  (CuO)  in  alkaline  solution  by  glucose  to  red  cuprous 
oxide  (Cu2O)  or  yellow  cuprous  hydroxide  (Cu2(OH)2). 
^xA-lbumin  must  be  removed  from  the  urine   before  making 
Trommer's  or  Fehling's  test. 

To  about  5  c.c.  of  the  urine  about  one-fourth  its  volume  of 
sodium  or  potassium  hydroxide  solution  is  added.  Then,  dr0p 
by  drop,  a  solution  of  cupric  sulphate  (about  10  per  cent,  solu- 
tion) is  added  and  the  liquid  is  agitated  until  the  bluish-white 
precipitate  of  cupric  hydroxide  (Cu(OH)2)  which  first  appears 
ceases  to  be  dissolved  and  the  liquid  presents  a  slightly  turbid 
or  opaque  appearance.  If  on  the  addition  of  cupric  sulphate 
the  bluish-white  precipitate  of  cupric  hydroxide  should  dis- 
solve on  agitating  the  liquid  and  impart  a  purplish  color  to 
the  liquid  instead  of  a  pure  blue,  it  may  be  taken  as  a  fair 
indication  of  the  presence  of  glucose.  The  liquid  is  heated  and 


NOTES  ON  CHEMICAL   LECTURES.  95 

if  glucose  be  present  the  cupric  oxide  will  be  reduced  to  red 
or  brownish-red  cuprous  oxide  or  yellow  cuprous  hydroxide. 

Delicacy  of  the  test,  0.01  per  cent,  of  glucose  in  the  urine. 

The  cupric  sulphate  solution  must  never  be  added  to  urine 
containing  sodium  hydroxide  while  hot,  or  black  cupric  oxide 
will  be  produced. 

Uric  acid  has  the  property  of  reducing  cupric  oxide  in  alka- 
line solution  to  cuprous  oxide. 

Creatinine  has  the  property  of  reducing  cupric  oxide  to 
cuprous  oxide  and  redissolving  the  latter. 

If  on  the  addition  of  one  drop  of  cupric  sulphate  solution 
to  the  urine  rendered  alkaline,  and  agitating  the  liquid,  the 
bluish-white  precipitate  of  cupric  hydroxide  is  dissolved,  the 
presence  of  glucose  may  be  inferred. 

If  the  liquid  is  heated  to  the  boiling-point,  and  glucose  be 
present,  cuprous  oxide  should  appear.  The  test,  however, 
may  fail  to  give  visible  cuprous  oxide,  or  cuprous  hydroxide 
even  though  glucose  be  present. 

In  such  a  case  several  drops  (3  to  6)  of  cupric  sulphate 
solution  are  added  to  a  fresh  mixture  of  urine  and  sodium 
hydroxide,  and  the  liquid  agitated.  If  the  bluish-white  pre- 
cipitate is  dissolved  the  addition  of  the  cupric  sulphate  is 
continued  until  the  liquid  presents  a  slightly  turbid  or  opaque 
appearance.  On  heating  the  liquid,  if  glucose  be  present,  a 
precipitate  of  cuprous  oxide  or  hydroxide  should  appear. 

If  the  bluish-white  precipitate  of  cupric  hydroxide  produced 
on  adding  a  few  drops  of  cupric  sulphate  solution  does  not 
wholly  dissolve,  and  on  heating  the  liquid  cuprous  oxide  or 
hydroxide  fails  to  appear,  it  may  be  concluded  that  glucose  is 
not  present.  Its  presence,  however,  is  to  be  suspected  when 
the  specific  gravity  of  the  urine  is  high  and  the  cupric  hydrox- 
ide is  dissolved. 

If  the  cupric  hydroxide  is  dissolved,  and  heating  the  liquid 
fails  to  give  cuprous  oxide  or  hydroxide,  glucose  may  still  be 
present,  especially  if  the  urine  possesses  a  high  specific  gravity. 

A.  If  more  than  5  to  10  drops  cupric  sulphate  solution  are 
required  to  produce  the  turbidity,  a  fresh  portion  of  the  urine 
is  diluted  with  \  or  9  volumes  of  water  and  Trommer's  test 
(adding  sodium  hydroxide  and  5  to  10  drops  of  cupric 


96  NOTES  ON  CHEMICAL  LECTURES. 

sulphate)  is  applied.  If  the  cupric  hydroxide  wholly  dissolves 
and,  on  heating,  unsatisfactory  results  are  obtained,  a  portion 
of  the  fresh  urine  is  more  largely  diluted  with  water,  and  the 
test  again  applied. 

'  B.  If  the  results  obtained  by  the  foregoing  methods  are  not 
satisfactory,  as  may  be  the  case  even  when  glucose  is  present 
in  large  quantity,  a  portion  of  Fehling's  solution  is  diluted 
with  about  4  volumes  of  water,  heated  to  the  boiling-point, 
and  several  drops  of  the  suspected  urine  added  to  the  hot 
diluted  Fehling's  solution.  This  test  may  fail  even  when 
glucose  is  present,  but  the  results  are  generally  satisfactory. 

C.  If  the  results  are  still  unsatisfactory,  the  urine  is  passed 
through  animal  charcoal  and  the  filtrate  tested  for  glucose. 

D.  Bruecke's  lead  process  for  the  removal  of  interfering 
substances  from  the  urine. 

If  the*  results  are  unsatisfactory,  after  having  followed  the 
foregoing  directions,  the  urine  is  examined  by  the  lead  process. 

Lead  process  :  50  c.c.  of  the  urine  are  treated  with  60  c.c. 
of  about  10  per  cent,  solution  of  commercial  plumbic  acetate, 
which  precipitates  the  sulphates,  phosphates,  carbonates, 
coloring-matter,  and  some  of  the  uric  acid  and  creatinine. 
The  liquid  is  filtered  and  the  precipitate  is  washed  once  or 
twice  with  water.  Excess  of  ammonium  hydroxide,  which 
precipitates  the  glucose  in  combination  with  lead  as  plumbic 
saccharate  (PbO)3(C6H12O6)2,  is  added  to  the  filtrate. 

The  precipitate  is  collected  on  a  filter  and  washed  until  free 
from  ammonia.  The  filter  paper  is  pierced  with  a  glass  rod 
and  the  precipitate  is  washed  through  the  aperture  into  a 
beaker  placed  under  the  funnel.  A  stream  of  hydrogen  sul- 
phide (H2S)  is  passed  through  the  mixture  until  all  of  the  lead 
is  precipitated  as  black  plumbic  sulphide  (PbS). 

The  black  plumbic  sulphide  is  filtered  off  and  the  precipitate 
washed  once  or  twice  with  water.  The  filtrate,  with  wash- 
water,  is  evaporated  to  a  volume  of  about  25  c.c.,  or  until  free 
from  hydrogen  sulphide. 

a.  Trommer's  test  is  applied  to  5  or  6  c.c.  of  the  liquid. 

b.  Fehling's  test  is  applied  to  another  portion. 

After  subjecting  normal  urine  to  the  lead  process  and  testing 
the  final  solution,  a  slight  reduction  of  the  cupric  oxide  may 


• 


NOTES  ON  CHEMICAL  LECTURES.  97 

occur,  due  to  the  presence  of  a  small  quantity  of  uric  acid 
which  may  have  escaped  removal  in  the  process.  This 
probably  is  the  reason  for  the  statement  that  glucose  is  a 
normal  constituent  of  urine.  The  final  solution  may  be 
allowed  to  stand  twenty-four  or  forty-eight  hours  and  the  uric 
acid  will  separate  in  crystals,  which  may  be  filtered  off  and 
the  tests  for  glucose  applied  to  the  filtrate,  or  the  final  solu- 
tion is  evaporated  to  dryness  on  a  water-bath,  the  glucose 
is  dissolved  from  the  residue  with  alcohol,  the  liquid  is 
filtered,  the  alcohol  solution  evaporated  to  dryness  on  a 
water-bath,  the  residue  dissolved  in  about  25  c.c.  of  water  and 
Trommer's  and  Fehling's  tests  applied  to  portions  of  the 
solution. 

An  inconstant  loss  of  about  50  per  cent,  of  the  glucose 
occurs  in  the  course  of  the  lead  process. 

6.  Fehling's  test :  Depends  upon  the  reduction  of  cupric 
oxide  (CuO)  in  alkaline  solution  by  glucose  to  red  cuprous 
oxide  (Cu2O)  or  yellow  cuprous  hydroxide  (Cu2(OH)2). 

Fehling's  solution  must  always  be  tested  before  being  used, 
by  diluting  it  with  about  four  volumes  of  water  and  heating  to 
the  boiling-point.  If  it  has  undergone  decomposition,  a  reduc- 
tion of  the  cupric  oxide  with  the  separation  of  cuprous  oxide 
or  hydroxide  will  occur  on  heating  the  diluted  solution. 

Fehling's  solution  which  has  undergone  decomposition  is 
unfit  for  use. 

Application  of  Fehling's  test :  About  1  c.c.  of  Fehling's 
solution  is  diluted  with  about  4  c.c.  of  water  and  heated  to  the 
boiling-point,  and  the  urine,  2  or  3  drops  at  a  time,  is  added 
to  the  liquid  which  is  heated  to  the  boiling-point  after  each 
addition  of  urine. 

If  glucose  be  present  reduction  will  occur,  and  a  precipitate 
of  red  cuprous  oxide  or  yellow  cuprous  hydroxide  will  be 
formed. 

Delicacy  of  the  test,  0.001  per  cent,  glucose  or  one  part  of 
glucose  in  60,000  parts  of  dilution. 

Often  in  applying  Trommer's  test  and  also  Fehling's  test  to 
the  urine,  a  brownish-red  flocculent  precipitate,  due  to  phos- 
phates, is  produced.  This  is  often  mistaken  for  cuprous  oxide 
and,  in  consequence,  glucose  believed  to  be  present  in  the 


98  NOTES  ON  CHEMICAL  LECTURES. 

specimen  of  urine.  In  differentiating  between  the  precipitate 
caused  by  phosphates  and  the  precipitate  of  cuprous  oxide 
caused  by  the  presence  of  glucose  it  may  be  observed,  that 
the  precipitate  of  phosphates  is  flocculent,  is  unevenly  distrib- 
uted throughout  the  liquid,  settles  to  the  bottom  slowly  and 
does  not  form  a  compact  layer  at  the  bottom  of  the  tube.  The 
precipitate  of  cuprous  oxide  is  not  flocculent,  is  evenly  dis- 
tributed throughout  the  liquid,  settles  to  the  bottom  rapidly 
and  forms  a  compact  layer  at  the  bottom  of  the  tube. 

A  considerable  number  of  substances  occur  under  normal 
or  pathological  conditions  in  the  urine  which  possess  the 
.property  of  reducing  cupric  oxide  in  alkaline  solution  (Trom- 
mer's  and  Fehling's  tests),  such  as  uric  acid,  creatinine, 
creatine,  allantoin,  mucin,  milk  sugar,  pyro-catechin,  hydro- 
chinon,  glycuronic  acid,  bile  coloring-matters,  and  homo- 
gentisic  acid. 

Homogentisic  acid,  C8H8O4,  may  be  detected  in  urine  by 
placing  the  urine  in  a  test-tube,  rendering  it  alkaline  by  the 
addition  of  sodium  hydroxide,  closing  the  tube  with  the  thumb 
and  shaking  the  tube  so  that  the  liquid  is  brought  intimately 
in  contact  with  the  air  in  the  tube.  In  the  presence  of  homo- 
gentisic  acid  oxidation  products  will  be  formed  and  the  liquid 
will  become  brown  or  black  in  color  depending  upon  the 
quantity  of  homogentisic  acid  present.  (Pyrocatechin  and 
hydrochinon  respond  in  a  similar  manner  to  the  test.) 

On  the  ingestion  of  certain  compounds,  such  as  benzoic 
acid,  salicylic  acid,  balsam  copaiba,  oxalic  acid,  oil  of  turpen- 
tine, glycerine,  chloral  and  chloroform,  substances  appear  in 
the  urine  which  possess  the  property  of  reducing  cupric  oxide 

in  alkaline  solution. 
y 

7.  Test  with  phenylhydrazine  hydrochloride  (C6H8N.,HC1  or 

C6H5NHNH2HC1)  (Fischer's  test,  1883):  Depends  upon  the  formation  of  a 
crystalline  compound,  phenylglukosazon,  when  phenylhydrazine  hydrochloride 
is  brought  in  contact  with  glucose.  The  compound  usually  separates  in  rosettes 
composed  of  yellow  needle-shaped  crystals,  which  melt  at  a  temperature  of  204° 
to  205°  C. 

Twice  as  much  phenylhydrazine  hydrochloride  as  will  cover  the  end  of  a  pen- 
knife-blade is  placed  in  a  test-tube  and  also  into  the  same  tube  three  times  as  much 
sodium  acetate  as  will  cover  the  end  of  a  penknife-blade  is  placed.  The  test-tube 
is  filled  to  about  one-third  its  capacity  with  water,  the  liquid  slightly  warmed,  and 
a  volume  of  the  urine  equal  in  volume  to  the  liquid  in  the  tube  is  added. 


NOTES  ON  CHEMICAL  LECTURES.  99 

The  tube  containing  the  mixture  is  placed  during  fifteen  or  twenty  minutes  in 
boiling  hot  water,  and  then  in  a  vessel  containing  cold  water. 

If  the  urine  contain  a  considerable  quantity  of  glucose  a  yellow  crystalline  pre- 
cipitate (C6H10O4(N2HC6H.).2  phenylglukosazon)  will  almost  immediately  appear. 

Sometimes  the  precipitate  may  appear  amorphous  macroscopically,  and  in  such 
cases  should  be  examined  microscopically. 

If  the  urine  contain  a  small  quantity  of  glucose,  the  liquid  in  the  test-tube 
should  be  emptied  into  a  conical  glass  and  the  sediment  examined  microscopically 
for  yellow,  needle-shaped  crystals.  The  occurrence  of  rather  large  yellow  plates 
or  brown  globules  does  not  indicate  the  presence  of  glucose. 

Albumin  does  not  interfere  with  this  test,  but  if  it  be  present  in  large  quantity 
it  is  better  to  remove  the  greater  part  of  it  by  boiling  and  filtering. 

This  test  is  unreliable  as  Fischer  himself  has  found  that  other  substances  in  the 
urine  will  yield  yellow  condensation  products  with  phenylhydrazine. 

3.  Molisch's  tests  : 

a.  Test  with  alpha-naphthol  (C10H7OH). 
Alpha-naphthol  is  a  derivative  of  naphthalene. 

H        H 

I  i 

C         C 

//   \/    ^ 
H— C       C       C— H 

|         ||         |          •=  naphthalene. 
H— C       C       C— H 

^   /\    // 
C        C 

I      I 

H        H 

H      OH 

I  I 

C         C 

^  \/  ^ 

H— C       C       C— H 

|  |  =  alpha-naphthol. 

H— C       C       C— H 

^   /\   // 
C        C 

H        H 

The  urine  is  diluted  with  water  (about  100  of  water  to  1  of  urine),  and  to  1  or 
2  c.c.  of  the  dilute  urine  2  drops  of  a  15  or  20  per  cent,  alcoholic  alpha-naphthol 
solution  are  added.  (The  liquid  may  become  turbid  owing  to  the  separation  of 
some  of  the  alpha-naphthol.)  A  quantity  of  concentrated  sulphuric  acid  equal  to 

13 


ICO  NOTES  ON  CHEMICAL  LECTURES. 

the  volume  of  liquid  in  the  test-tube  is  added,  and  if  glucose  be  present  a  deep 
violet  color,  transitory  in  nature,  will  be  produced.  On  diluting  the  liquid  with 
water  a  bluish-violet  precipitate  will  be  formed. 

Delicacy  of  the  test,  0.00001  per  cent,  of  glucose  (1  part  glucose  in  10,000,000 
parts  of  water). 

The  test  is  not  very  reliable  when  applied  to  the  urine. 

b.  Test  with  thymol  (C,0HUO  =  C6H3CH3C3H.OH,  methylpropylphenol). 

The  test  is  performed  in  a  manner  similar  to  the  alpha-naphthol  test. 

The  urine  is  considerably  diluted  with  water  (1-100),  and  to  1  or  2  c.c.  of  the 
liquid  2  drops  of  a  15  or  20  per  cent,  alcoholic  thymol  solution  are  added.  A 
quantity  of  concentrated  sulphuric  acid  equal  in  volume  to  the  liquid  in  the  test- 
tube  is  added  and,  if  glucose  be  present,  a  deep  cinnabar-red  color  will  be  pro- 
duced, quickly  changing  to  ruby-red,  and  then  to  carmine.  On  diluting  with 
water  the  carmine  color  remains. 

Delicacy  of  the  test,  the  same  as  the  alpha-naphthol  test. 

The  test  is  not  very  reliable  when  applied  to  the  urine. 

Both  of  Molisch's  tests  fail  to  give  a  reaction  with  urea,  uric  acid,  hippuric  acid, 
creatinine,  allantoin,  pyro-catechin,  and  indican. 

With  cane  sugar,  fruit  sugar,  and  maltose  both  these  tests  give  reactions  similar 
to  those  with  glucose. 

QUANTITATIVE  DETERMINATION  OF  GLUCOSE  IN  URINE. 

1.  Fermentation  method  by  loss  in  weight  :  Depends  upon  the  fermenta- 
tion of  glucose  in  the  urine,  thereby  causing  a  loss  in  the  weight  of  the  urine, 
due  to  the  formation  of  alcohol  and  the  escape  of  carbon  dioxide. 

180.  92.  88. 

C6H12O6  =±  2C2H5OH  +  2CO2 

Theoretically,  in  fermentation,  180  parts  glucose  evolve  92  parts  alcohol  and  88 
parts  carbon  dioxide.  Hence  1  part  by  weight  of  carbon  dioxide  lost  is  equivalent 
to  the  fermentation  of  2.045  parts  of  glucose. 


CO».        CeHi,06.        CO.,.        C6H]2O6. 

88    :     180     ::     1     :     2.045 

Method  :  50  c.c.  of  urine  are  placed  in  a  small  flask,  and  a  small  portion  of 
yeast  is  added.  The  flask  is  closed  with  a  perforated  cork  to  which  a  small  calcium 
chloride  tube  is  attached  (to  collect  moisture). 

The  entire  apparatus  is  weighed  and  stood  aside  in  a  warm  place  that  the  glucose 
may  ferment. 

When  the  fermentation  is  completed,  the  cork  is  taken  out  of  the  bottle,  and,  by 
means  of  a  glass  tube,  the  carbon  dioxide  which  may  occupy  the  air-space  in  the 
flask,  is  sucked  out.  The  cork  is  replaced  and  the  entire  apparatus  is  weighed. 
Each  gramme  lost  is  equivalent  to  2.045  grm.  glucose.  To  obtain  the  percentage 
of  glucose,  50  c.c.  of  urine  having  been  used,  the  result  must  be  multiplied  by  2. 

Water  dissolves  its  own  volume  of  carbon  dioxide,  therefore  the  50  c.c.  of  liquid 
holds  in  solution  50  c.c.  of  carbon  dioxide,  which  is  weighed  with  the  apparatus, 
and  thus  causes  an  error  by  adding  excess  of  weight  equal  to  the  weight  of  the 
carbon  dioxide  retained  by  the  liquid. 


o  : 


NOTES  ON  CHEMICAL  LECTURES.  101 

To  correct  this  error,  the  weight  of  50  c.c.  of  carbon  dioxide  must  be  added  to 
the  loss  of  weight  before  multiplying  by  the  factor  2.045. 

1  c.c.  CO2  weighs  0.001971  grm. 
50  X  0.001971  =  0  0985  grm. 

Example  :  Weight  of  apparatus  before  fermentation,  67.6  grm. 
"  «          after  "  65.6     " 

2.0     "     loss  in  weight. 
-f  weight  of  50  c.c.  CO2  =  0  0985 
2.0985 

2.0985  X  2.045  =  4.29  grm.  glucose  in  50  c.c.  urine ;  then  to  obtain  the  percentage 
(quantity  in  100  c.c.  urine), 

2  X  4.29  =  8.58  per  cent,  glucose. 

Instead  of  the  foregoing  the  correction  may  be  made  by  adding  the  number  0.4 
to  the  apparent  percentage.  0.4  grm.  glucose  will  evolve  0.1955  grm.  CO2,  or 
sufficient  CO2  to  saturate  100  c.c.  water. 

Glucose.      Carbon  dioxide.      Glucose.      Carbon  dioxide. 

1.          180         :       88       •:        0.4      :      0.1955  grm. 


2. 


CO2.  CO*  CO2.  CO2. 

22320  c.c.  :  44  grm.  :;  100  c.c.  :  0.1971  grm. 


The  50  c.c.  liquid  absorbed  50  c.c.  CO2,  or  50  X  0.001971  grm.  =  0.0985  grm. 
CO2,  and  as  the  calculation  is  made  on  the  basis  of  100  c.c.  of  liquid,  2  X  0.0985 
=  0.1971  grm.  CO2  in  100  c.c.  liquid,  equivalent  to  0.4  grm.  glucose. 

The  first  of  the  foregoing  proportions  shows  that  0.1955  grm.  CO2  is  evolved 
from  0.4  grm.  glucose,  and  as  0.1971  grm.  excess  of  weight  of  CO2  is  retained  by 
100  c.c.  of  liquid,  the  loss  is  compensated  by  adding  the  fixed  number  0.4  to  the 
apparent  percentage. 

Example  :  Weight  of  apparatus  before  fermentation,  67.6  grm. 
"  "          after  "  65.6     " 

2.0     "     loss  in  weight. 
Then 

2  grm.  X  2.045  =  4.090  grm.  X  2  =  8.18 

Of- 

8.58  per  cent,  glucose. 

To  obtain  percentage  in  100  parts  by  weight  of  urine. 
Example : 

Spec.  grav.  of  urine.        Spec.  grav.  of  water. 

1033  :  1000        ::        8.58        :        X 

2.  Roberts'  differential  density  method  for  the  deter- 
mination of  glucose  in  urine :  Depends  upon  the  loss  in 
specific  gravity  of  the  urine,  due  to  the  fermentation  of  glucose 
with  the  formation  of  alcohol,  and  evolution  of  carbon  dioxide. 


102  NOTES  ON  CHEMICAL  LECTURES. 

Each  degree  in  specific  gravity  lost  is  equivalent  to  1  grain 
of  glucose  in  437.5  grains  (one  imperial  fluid  ounce)  of  urine. 
Or  referred  to  percentage  by  volume  : 

437.5  :  1   ::   100  :  0.23  per  cent. 

Therefore  one  degree  of  specific 'gravity  lost  is  equivalent 
to  0.23  per  cent,  of  glucose. 

Method :  To  60  or  70  c.c.  of  urine  a  small  quantity  of  yeast 
is  added  and  the  liquid  stood  aside  in  a  moderately  warm 
place  to  ferment.  As  a  control  test  another  portion  of  60  or 
70  c.c.  of  the  same  urine  is  taken  and  stood  aside  without  the 
addition  of  yeast. 

When  the  fermentation  is  completed  the  specific  gravities  of 
the  fermented  and  unfermented  urines  are  taken  separately. 
The  specific  gravity  of  the  fermented  urine  is  deducted  from 
the  specific  gravity  of  the  unfermented  urine,  and  the  result  is 
multiplied  by  the  factor  0.23.  The  result  of  the  multiplication 
will  be  the  percentage  of  glucose. 

This  method  is  the  one  most  easily  performed  by  the  physi- 
cian and  affords  fairly  accurate  results. 

3.  Fehling's  method :  Depends  upon  the  reduction  of 
cupric  oxide  in  alkaline  solution  by  glucose  to  cuprous 
oxide. 

Fehling's  solution  is  prepared  so  that  1  c.c.  of  it  shall  equal 
0.005  grm.  glucose, — /.  e.,  0.005  grm.  glucose  will  be  required 
to  reduce  the  cupric  oxide  in  1  c.c.  of  the  solution  to  cuprous 
oxide. 

Preparation  of  the  solution  :  5  molecules  of  crystallized 
cupric  sulphate  are  reduced  to  cuprous  oxide  by  1  molecule 
of  glucose. 

Then 

CeHjoOg.        5CuSO4  +  5H2O.        Glucose.  Cupric  sulphate. 

180     :      1247.5      ::       5  grm.     :     34.652  grm. 

Therefore  34:.652  grm.  cupric  sulphate  will  be  reduced  by  5 
grm.  glucose. 

The  cupric  sulphate  crystals,  before  being  weighed,  should 
be  deprived  of  water,  held  mechanically,  by  being  crushed  and 
dried  between  bibulous  paper. 


^dr2Va 


k  J 

*£k  £  V  ^-^f  (Cj(*J£  ft  i  <™-*>  ^t^ 


&,>  -~^JU    jfM*Ji^  -  ^  y'<0 


/  /.  J 


NOTES  ON  CHEMICAL  LECTURES.  103 

One  molecule  of  glucose  is  equivalent  to  5  molecules  of 
cupric  sulphate,  CuSO4  -f~  5H2O. 

One  molecule  of  glucose  is  equivalent  to  5  molecules  of 
cupric  oxide,  CuO. 

A.  34.652  grm.  pure  crystallized  cupric  sulphate  are  dissolved 
in  about  200  c.c.  water. 

B.  About  J  73  grm.  sodic  potassium  tartrate  (KNaC4H4O6) 
(Rochelle    salt)   are   dissolved   in   about   480  c.c.  of   sodium 
hydroxide  solution  of  1.14  specific  gravity.     The  cupric  sul- 
phate solution  is  slowly  added  to  the  Rochelle  salt  solution } 
at  the  same  time  the  solution  is  constantly  stirred. 

The  bluish-white  precipitate  of  cupric  hydroxide  which 
appears  will  be  completely  dissolved  by  the  liquid. 

The  object  of  the  Rochelle  salt  is  to  hold  the  cupric 
hydroxide  in  solution. 

The  blue  liquid  is  diluted  with  water  to  1000  c.c.,  then 

1000  c.c.  =  5.0      grm.  glucose. 
10  c.c.  =  0.050      " 
1  c.c.  =  0.005      " 

Fehling's  solution  is  prone  to  undergo  spontaneous  de- 
composition. It  may,  however,  be  preserved  so  as  to  avoid 
its  undergoing  decomposition  by  keeping  the  cupric  sulphate 
and  Rochelle  salt  solutions  separately  and  mixing  equal 
volumes  of  the  two  solutions  when  needed,  viz. : 

34.652  grm.  cupric  sulphate  are  dissolved  in  water  and 
diluted  to  500  c.c.  The  Rochelle  salt  solution  is  also  diluted 
with  water  to  500  c.c.  The  two  solutions  must  be  kept  in 
separate  bottles  closed  with  rubber  stoppers. 

To  employ  the  solutions  :  1  volume  of  the  cupric  sulphate 
solution  is  mixed  with  an  equal  volume  of  Rochelle  salt 
solution. 

Example : 

5  c.c.  cupric  sulphate  solution. 
_5  c.c.  Rochelle  salt 
10  c.c.  Fehling's  " 

The  accuracy  of  the  solution  may  be  determined  by  titering 
it  with  a  standard  solution  of  glucose,  prepared  by  dissolving 
0.5  grm.  glucose  in  100  c.c.  water. 


104  NOTES  ON  CHEMICAL  LECTURES. 

The  cupric  oxide  in  10  c.c.  Fehling's  solution  should  be 
exactly  reduced  by  10  c.c.  of  the  glucose  solution. 

In  using  Fehling's  solution  the  glucose  solution  must  be 
added  to  the  Fehling's  solution,  and  not  the  Fehling's  to  the 
urine. 

If  the  diabetic  urine  have  a  specific  gravity  of  about  1035, 
it  should  be  diluted  with  4  volumes  of  water, — /.  e.,  10  c.c.  of 
urine  +  40  c.c.  of  water. 

If  the  diabetic  urine  have  a  specific  gravity  of  about  1040, 
it  should  be  diluted  with  9  volumes  of  water, — i.  e.,  10  c.c.  of 
urine  -f-  90  c.c.  of  water. 

Albumin,  if  present  in  the  urine,  must  previously  be  re- 
moved by  coagulation  and  filtration  as  it  interferes  with 
Fehling's  test. 

Method :  10  c.c.  of  Fehling's  solution  (=  0.050  grm. 
glucose)  are  placed  in  a  beaker  or  dish  and  diluted  with  about 
40  c.c.  of  water  and  the  liquid  is  heated  to  the  boiling-point. 
If  necessary,  the  urine  should  be  diluted  with  4  or  9  volumes  of 
water  then  placed  in  a  burette.  From  0.5  to  1.0  c.c.  at  a  time 
of  the  liquid  in  the  burette  should  be  run  into  the  hot  diluted 
Fehling's  solution.  Heat  is  applied  to  the  Fehling's  solution 
after  each  addition  of  urine  to  keep  it  at  about  the  boiling- 
point.  The  addition  of  the  urine  to  the  hot  Fehling's  solu- 
tion is  continued  until  the  reduction  of  the  cupric  oxide  is 
completed.  This  is  recognized  by  the  complete  disappearance 
of  the  blue  color  of  the  liquid. 

As  the  point  of  complete  reduction  is  approached,  the  pre- 
cipitate of  cuprous  oxide  will  subside  more  rapidly,  thereby 
allowing  the  easy  observance  of  the  disappearance  of  the  blue 
color  of  the  liquid. 

The  first  titration  usually  gives  only  approximate  results 
unless  performed  with  the  greatest  care.  A  second  titration 
should  be  made,  in  which  the  urine  (from  0.5  to  1.0  c.c.  at  a 
time)  is  run  into  the  hot  Fehling's  solution  until  the  quantity 
added  is  about  1  c.c.  less  than  that  employed  in  the  first  titration. 
The  addition  of  the  urine,  in  small  portions,  is  continued  until 
the  blue  color  of  the  liquid  is  completely  discharged. 

Example :  Suppose  the  urine  employed  had  been  diluted 
in  the  proportion  of  1  volume  urine  to  9  volumes  water,  and 


0     J   IW  0     (,0*L 
4  £   O     V 


U 

—i  — 


NOTES  ON  CHEMICAL  LECTURES.  105 

8  c.c.  of  this  diluted  urine  had  been  required  to   reduce  the 
cupric  oxide  in  10  c.c.  Fehling's  solution. 

One-tenth  of  the  8  c.c.  of  liquid  was  urine,  and  must  have 
contained  0.050  grm.  glucose  (the  quantity  of  glucose  required 
to  reduce  10  c.c.  Fehling's  solution). 

Urine.  Glucose.  Urine.  Glucose. 

Then     0.8  c.c.   :   0.050  grm.  ::   100  c.c.  :  6.25  per  cent. 

The  process  should  be  performed  as  rapidly  as  is  consistent 
with  accuracy. 

If  the  urine  mixture  employed  contain  more  than  0.5  per 
cent,  glucose,  it  should  be  still  further  diluted  with  a  measured 
volume  of  water. 

If  albumin  be  present,  it  must  be  removed  before  making 
the  determination. 


CLINICAL  APPLICATION  OF  FEHLING'S  METHOD. 

i  c.c.  Fehling's  solution  =  0.005  grm-  glucose. 

a.  1  c.c.  of  Fehling's  solution  is  placed  in  a  test-tube  and 
diluted  with  4  c.c.  water  (or  5  c.c.  of  diluted  Fehling's  solution, 
consisting  of  1  c.c.  Fehling's  solution  and  4  c.c.  water). 

The  liquid  is  heated  to  the  boiling-point  and  1  c.c.  of  undi- 
luted urine  is  added  and  the  liquid  is  again  heated. 

If  the  blue  color  is  entirely  discharged,  0.5  per  cent,  or 
more  of  glucose  is  present. 

If  the  blue  color  is  not  entirely  discharged,  less  than  0.5  per 
cent,  of  glucose  is  present. 

b.  To  1  c.c.  Fehling's  solution  -j-  4  c.c.  water  heated  to  the 
boiling-point  0.1  c.c.  of  the  same  urine  is  added  and  the  liquid 
heated. 

If  the  blue  color  is  entirely  discharged,  5.0  per  cent,  or  more 
glucose  is  present. 

If  the  blue  color  is  not  entirely  discharged,  less  than  5.0  per 
cent,  glucose  is  present. 

If  the  color  is  not  discharged,  add  another  0.1  c.c.  urine  and 
again  heat  the  liquid. 

If  the  blue  color  is  entirely  discharged,  2.5  per  cent,  or  more 
glucose  is  present. 


106  NOTES  ON  CHEMICAL  LECTURES. 

If  the  blue  color  is  not  entirely  discharged,  less  than  2.5  per 
cent,  glucose  is  present. 

The  addition  of  the  urine  0.1  c.c.  at  a  time,  keeping  account 
of  the  quantity  added,  and  heating  the  liquid  is  continued  until 
the  blue  color  is  discharged. 

c.  1  c.c.  of  Fehling's  solution  is  placed  in  a  test-tube  and 
diluted  with  4  c.c.  of  water  and  the  liquid  heated  to  the  boiling- 
point.  The  urine  is  added  from  a  pipette,  a  drop  at  a  time, 
(the  number  of  drops  added  is  noted?)  and  the  liquid  is  heated 
after  the  addition  of  each  drop.  This  addition  of  a  drop  at  a 
time  of  the  urine  and  heating  the  liquid  after  the  addition  ot 
each  drop  is  repeated  until  finally  the  blue  color  of  the  liquid 
has  disappeared.  As  two  drops  of  urine  are  approximately 
equal  to  0.1  c.c.,  therefore,  the  number  of  drops  employed 
divided  by  2  will  approximately  furnish  the  number  of  tenths 
of  a  cubic  centimetre  employed.  In  calculating  results  the 
following  rule  should  be  used. 

Rule :  Divide  the  number  5  by  the  number  of  tenths  of 
urine  employed  converted  into  whole  numbers.  The  result 
will  be  the  approximate  percentage  of  glucose. 

To  obtain  more  accurate  results,  the  urine  should  be  diluted 
and  titered  in  the  usual  manner  with  10  c.c.  Fehling's  solution 
-j-  40  c.c.  water. 

Percentage  amount  of  glucose  present  in  urine,  as  in- 
dicated by  the  quantity  of  the  urine  required  to  exactly 
decolorize  i  c.c.  of  Fehling's  standard  solution  diluted 
with  4  c.c.  of  water. 

OF  UNDILUTED  URINE. 


0.1  (5  -=-  1) 5.0 

0.12  . 4.2 

0.14 3.5 

0.16  .    . 3.1 

0.18 2.7 

0.2 2.5 

0.25 2.0 

0.3 1.66 

0.35  .  1.4 


c.c.  urine. 

0.4     .... 

Glucose, 

per  cent. 

.    .    .    .     1.25 

0.45  .... 

....    1  10 

05     .... 

.    .    .    .    10 

06     .... 

.    ...    083 

0.7     .... 

....    0.71 

0.8     .... 

.    .    .    .    0.62 

09     .... 

.    .    .    .    0-55 

1.0 

0.5 

NOTES  ON  CHEMICAL  LECTURES.  107 

OF  DILUTED  URINE  (i  to  10). 


c.c.  urine. 

0.4  (50  ~  4) 
0.5     .... 

Glucose, 
per  cent. 

.    .    .    .  12.5 
.    .    .    .100 

0.6     .... 

.    .    .    .    833 

0.7     .... 

.    .    .    .    7.14 

0.8     .... 

.    .    .        625 

0.9     .... 

.    ...    555 

1.0     .... 

.    ...    50 

1.2     ... 

.    ...    4.2 

1.4     .... 

.    ...    35 

1.6     .    .    .    . 

.    ...    31 

1.8     .... 

.    ...    27 

2.0     .... 

.    ...    2.5 

2.25   . 

2.2 

Glucose, 

per  cent. 

2.50  .    .    .    . 

....  2.0 

2.75  .    .    .    . 

....  1.8 

3.00  .    .    .    . 

....  1.6 

3.5     .    .    .    . 

.    .1.4 

4.0     .    .    .    . 

....  1.25 

4.5     .    .    .    . 

....  1.1 

5.0     .    .    .    . 

....  1.0 

6.0     .    .    .    . 

....  0.83 

7.0  '  .    .    .    . 

....  0.7 

8.0     .    .    .    . 

....  0.6 

9.0     .    .    .    . 

....  0.55 

10.0 

.  0.5 

4.  Determining  glucose  quantitatively  by  means  of  the 
saccharimeter :  If  light  which  has  undergone  double  refrac- 
tion, as  in  passing  through  a  crystal  of  Iceland  spar,  is  exam- 
ined with  an  analyzer,  it  is  found  that  both  the  ordinary  and 
extraordinary  rays  are  completely  polarized  at  right  angles  to 
each  other.  Advantage  is  taken  of  this  in  the  construction  of 
the  saccharimeter  or  polariscope. 

When  20.51  grm.  anhydrous  glucose  are  dissolved  in 
water  and  diluted  to  100  c.c.,  and  an  observation-tube  200 
mm.  in  length  filled  with  the  solution  is  placed  in  Laurent's 
saccharimeter,  the  ray  of  light  will  be  deflected  to  the 
right  100  markings  or  divisions  as  indicated  on  the  vernier- 
scale. 

Hence 

100  divisions  on  the  scale  =  20.51       grm.  glucose. 
1  division  "      =    0.2051     " 

Method ;  100  c.c.  urine  are  mixed  with  10  c.c.  basic 
acetate  of  lead  (Pb3O2(C2H3O2)2)  solution,  and  filtered  through 
a  filter  which  has  not  been  previously  moistened  with  water. 
A  200  mm.  (standard)  observation-tube  is  filled  with  the 
filtrate. 

14 


108  NOTES  ON  CHEMICAL  LECTURES. 

The  field  of  vision  in  the  saccharimeter  must  be  homoge- 
neous in  color,  and  the  zero  divisions  on  the  vernier  must 
correspond  before  the  tube,  is  placed  in  the  saccharimeter. 

The  observation-tube  containing  the  urine  is  placed  in  the 
saccharimeter,  and  the  effect  on  the  field  of  vision  is  noted. 
If  the  urine  contain  glucose,  one-half  of  the  field  of  vision 
will  be  darker  than  the  other  half.  The  large  thumb-screw  is 
then  rotated  until  the  field  of  vision  again  becomes  homoge- 
neous in  color. 

The  reading  on  the  vernier  is  noted.  As  the  urine  was 
diluted  one-tenth  by  the  lead  solution,  the  reading,  therefore, 
is  one-tenth  too  low.  This  is  corrected  by  adding  one-tenth  of 
the  reading  to  the  reading.  The  corrected  reading  is  then 
multiplied  by  the  value  of  each  division  on  the  vernier, — 
namely,  0.2051  grm. 

Example  : 

Suppose  the  reading  was 2.3.1 

ytg-  of  the  reading  added  to  the  reading     .    2.31 

25.41 
25.41  X  0.2051  =  5.211  per  cent,  glucose. 

If  the  amount  of  glucose  in  the  urine  be  very  small,  a  400 
mm.  observation-tube  may  be  used.  In  such  an  event  the 
corrected  reading  must  be  divided  by  2  before  multiplying  by 


0.2051. 

RELATION  OF  SACCHAROSES  AND  AMYLOSES  TO  GLUCOSE^ 


Mol-wV?.(f 
Glucose,          C12H24O12(2C6H12O6),  =  360^=  100  glucose. 

Saccharoses,  C12H22On,  =  342^   95 

Amyloses,       C12H20O10(2C6H10O5),  =  324^£,  90 


SYNOPSIS  OF  ALBUMINS. 

1.  Native  albumins,  soluble  in  water. 

a.  Serum  albumin,  not  precipitated  by  ether. 
/;.  Egg  albumin,  precipitated  by  ether. 
c.  Peptones. 


NOTES  ON  CHEMICAL  LECTURES.  109 

2.  Globulins,  insoluble  in  water,  but  soluble  in  1  per  cent, 
solution  of  sodium  chloride. 

a.  Fibrinogen. 

b.  Fibrinoplastin. 

c.  Myosin. 

d.  Vitellin. 

e.  Crystallin. 

3.  Derived  "albumins  or  albuminates,  insoluble  in  water 
orjjdilute  sodium  chloride  solution,  but  soluble  in  acids  or 
gastric  juice. 

a.  Acid  albumin  (syntonin). 

b.  Alkali  albumin. 

c.  Casein. 

d.  Fibrin. 

c.  Coagulated  albumin. 
'/.  Amyloid  substance. 

ALBUAilE  IN  URINE. 

The  albumin  in  urine  in  Bright's  disease   is  serum  albumin. 

Serum  globulin  in  small  quantity  may  also  be  present. 

The  principal  forms  of  albumin  present  in  urine  are  serum 
albumin,  globulin,  hemialbumose  and  nucleo-albumin  (mucin). 

The  quantity  of  albumen  varies  from  a  slight  trace  to  3  per 
cent. 

Albuminous  urine  is  usually  pale  in  color  and  has  a  low 
specific  gravity  (1006  to  1014). 

QUALITATIVE  TESTS  FOR  ALBUMIN. 

1.  By  heating  the  urine  to  the  boiling-point  (boiling- 
test). 

a.  If  a  flocculent  precipitate  appear,  it  is  due  either  to  earthy 
phosphates  or  coagulated  albumin. 

The  warm  urine  in  which  precipitation  has  occurred  is 
treated  with  one  or  two  drops  of  nitric  acid.  If  the  precipitate 
be  dissolved  by  the  acid,  it  is  composed  of  phosphates  ;  if 
unclissolved,  it  is  albumin. 


110  .VOTES  ON  CHEMICAL  LECTURES. 

b.  If  no  precipitate  appear  on  boiling,  the  warm  urine  is 
treated  with  one  or  two  drops  of  nitric  acid,  and  if  albumin 
be  present  it  will  be  precipitated.  If  the  quantity  of  nitric 
acid  be  either  too  large  or  too  small  the  precipitation  of  the 
albumin  may  not  occur. 

Serum  albumin  and  globulin  respond  to  this  test.  Peptone 
does  not. 

If  the  precipitate  separates  only  after  cooling,  it  is  albumose. 

2^  Heller's  method. 

If  not  clear,  the  urine  must  be  filtered  before  making  the 
test. 

A  test-tube,  containing  strong  nitric  acid  to  the  depth  of  at 
least  an  inch,  or  better,  a  conical  glass,  containing  strong  nitric 
acid,  is  inclined  and  the  urine  is  slowly  poured  down  the  inner 
side  of  the  vessel  so  that  it  shall  form  a  layer  above  the  nitric 
acid.  If  albumin  be  present,  a  milky  zone  will  be  produced 
at  the  point  of  contact  of  the  two  liquids. 

Delicacy  of  the  test,  0.00*25  per  cent,  albumin. 

If  the  urine  contain  excess  of  urates  a  zone,  due  to  the  sepa- 
ration of  uric  acid,  may  be  formed.  This  zone  is  brownish-red 
in  color  (the  albumin  zone  is  white),  and  forms,  not  at  the 
point  of  contact  of  the  urine  and  acid,  but  some  distance 
above  the  point  of  contact  of  the  urine  and  acid.  The 
under  part  of  the  zone  is  not  so  sharply  defined  as  the 
albumin  zone.  If  in  doubt,  dilute  the  urine  nearly  one-half 
with  water  and  repeat  the  test.  In  the  diluted  urine  uric  acid 
will  not  interfere. 

In  the  presence  of  albumin  and  excess  of  urates  two  zones 
will  be  produced, — the  uric  acid  zone  above  the  albumin. 

On  the  administration  of  balsams — such  as  copaiba — a  sub- 
stance (abietic  acid)  appears  in  the  urine  which,  with  nitric 
acid,  forms  a  zone  similar  to  that  formed  by  albumin.  This 
substance  also  interferes  with  the  first  test,  by  separating  as  a 
flocculent  precipitate  on  boiling  the  urine.  The  precipitate  is 
soluble  in  alcohol,  albumin  is  not  soluble  in  alcohol. 

If  indican  be  present,  the  urine  will  become  violet  in  color 
at  the  point  of  contact  with  the  nitric  acid.  In  presence  of 
biliary  matter  it  will  become  green,  and  then  change  to  red- 
brown. 


NOTES  ON  CHEMICAL  LECTURES.  Ill 

J5.  Picric  acid  test  (C6H2(NOj3OH)  (carbazotic  acid)  Gal- 

lipe'.s  test).          \^JKA    llU^ljGVAM' 

If  the  urine  is  turbid,  it  must  be  filtered. 

a.  Urine  to  the  depth  of  an  inch  is  placed  in  a  test-tube  and 
a  saturated  aqueous  solution  of  picric  acid  is  slowly  poured 
down  the  side  of  the  tube  so  that  it  collects  as  a  distinct  layer 
above  the  urine.      If  albumin  be  present,  a  white  zone  will  be 
produced  at  the  point  of  contact  of  the  two  liquids. 

b.  Urine  is  added,  drop  by  drop,  to  a  saturated  solution  of 
picric  acid,  and,  if  albumin  be  present,  a  sharply  defined  tur- 
bidity will  be  produced  at  the  point  of  contact  of  the  drop  of 
urine  with  the  acid. 

jl.  Potassium  ferrocyanide  test :  If  the  urine  is  turbid,  it 
must  be  filtered.  ttWA  ^MJU&X  . 

The  urine  is  strongly  acidulated  with  acetic  acid  (to  1  vol- 
ume of  urine  add  about  \  volume  of  acid)  and,  without  heating, 
3  or  4  drops  of  potassium  ferrocyanide  solution  are  added. 

If  albumin  be  present,  a  turbidity  or  a  flocculent  precipitate, 
depending  upon  the  quantity  of  albumin,  will  be  produced. 

Delicacy  of  the  test,  0.0025  per  cent,  albumin. 

Serum  albumin,  globulin,  and  albumose  respond  to  the  test, 
but  peptone  does  not.  Nucleo-albumin  responds  to  the  test. 
Xucleo-albumin  may  be  removed  by  precipitating  with  plumbic 
acetate,  filtering,  removing  the  lead  from  the  filtrate  by  means 
of  hydrogen  sulphide  and  applying  the  ferrocyanide  test  to 
the  filtrate. 

5.  Trichloracetic  acid  test,  HCClgCCX  (Raabe).  5  c.c.  of 
urine  filtered  through  a  filter,  which  has  been  previously 
thoroughly  washed  with  water  to  remove  vegetable  albumin, 
are  placed  in  a  narrow  test-tube  and  a  piece,  about  the  size 
of  a  large  pea,  of  trichloracetic  acid  is  placed  in  the  urine.  In 
the  presence  of  albumin  a  white  zone  or  cloud  will  be  pro- 
duced at  the  point  where  the  resulting  solution  of  acid  comes 
in  contact  with  the  urine. 

Urine  containing  an  excess  of  uric  acid  may  produce  a 
diffuse  turbidity  which  disappears  on  heating  the  liquid.  This 
turbidity,  due  to  excess  of  uric  acid,  may  not  occur  if  the 
urine  be  previously  diluted  with  water.  Nucleo-albumin 
(mucin)  responds  to  the  test  and  as  nearly  every  normal  urine 


TPT 
^W^T 


112 


NOTES  ON  CHEMICAL  LECTURES. 


contains  more  or  less  nucleo-albumin  the  test  is  not  of  nuicli 
I'ahie — unless  the  nucleo-albumin  be  removed  by  precipitation 
with  plumbic  acetate,  etc.,  previous  to  applying  the  trichlor- 
acetic  acid  test. 

Jk_  Biuret  test  for  albumin  :  The  urine  is  rendered  alkaline 
with  sodium  or  potassium  hydroxide,  and  a  few  drops  of  dilute 
cupric  sulphate  solution  are  added.  If  albumin  be  present, 
the  precipitate  of  cupric  hydroxide  will  dissolve  on  shaking 
and  a  violet-red  color  will  be  imparted  to  the  liquid. 
Delicacy  of  test,  0.01  per  cent. 

Serum  albumin,  globulin,  albumose,  and  peptone  respond 
to  this  test. 

To  distinguish  between  serum  albumin,  globulin,  hemi- 
albumose  and  nucleo-albumin  (mucin). 

1.  The  cold  urine  is  treated  with  an  excess  of  acetic  acid. 


Serum  albumin.  Globulin.  Hemialbumose. 


Nucleo-albumin. 
(Afucin.) 


Not  Not  Not 

precipitated,     precipitated,     precipitated. 


2.  The  urine  is   filtered   and   solution  of  potassium  ferro- 
cyanide  is  added  to  the  cold  filtrate. 


Serum  albtimin.  Globulin.  Hemialbumose. 


Precipitated.    Precipitated. 


Precipitated. 


The  liquid  is  heated  to  the  boiling  temperature. 


Serum  albumin. 


Globulin.  Hemialbumose. 


Precipitate 

remains 
undissolved. 

Precipitate 
remains 
undissolved. 

Precipitate 
dissolved. 

NOTES  ON  CHEMICAL  LECTURES.  113 

To  separate  serum  albumin  from  globulin,  a  slight  excess 
of  ammonium  hydroxide  is  added  to  the  urine  to  precipitate 
the  phosphates  of  the  alkaline  earths.  After  the  liquid  has 
stood  several  hours  the  phosphates  are  filtered  off  and  the 
filtrate  is  treated  with  its  own  volume  of  a  saturated  solution 
of  ammonium  sulphate  which  will  precipitate  the  globulin 
leaving  the  serum  albumin  in  solution. 

QUANTITATIVE  DETERMINATION  OF  ALBUMIN  IN  URINE. 

1 .  By  weighing  ;  If  the  urine  is  turbid,  it  must  be  filtered. 
50  c.c.  or  100  c.c.  urine,  depending  upon  the  quantity  of 

albumin  present,  are  warmed  to  about  blood-heat  on  a  water- 
bath,  and  acetic  acid  added,  drop  by  drop,  until  the  albumin 
separates  in  flocculent  masses.  (The  acetic  acid  keeps  the 
earthy  phosphates  in  solution.)  The  liquid  is  heated  to  the 
boiling-point,  and  the  coagulated  albumin  is  collected  on  an 
equipoised  or  a  weighed  washed  filter  and  washed  with  water 
(portions  of  5  c.c.  at  a  time),  until  a  last  portion  of  filtrate 
coming  from  the  funnel  fails  to  respond  to  the  test  for  a 
chloride  with  argentic  nitrate,  or  a  drop  of  the  filtrate  fails  to 
leave  a  residue  when  evaporated  on  platinum  foil.  The  coag- 
ulated albumin  is  washed  while  on  the  filter  with  alcohol, 
the  two  (equipoised)  filters  separated  and  dried  at  a  temper- 
ature not  above  100°  C.,  and  weighed. 

The  weight  of  albumin  obtained  is  the  quantity  in  the 
volume  of  urine  employed. 

2.  Esbach's  method :  Depends  upon   the  precipitation  of 
albumin  by  picric  acid. 

The  quantity  of  albumin  is  determined  by  measuring  the 
height  of  the  precipitate  in  a  specially  graduated  tube,  Esbach's 
albuminimeter. 

The  picric  acid  solution  is  prepared  by  dissolving  10  grm. 
picric  acid  and  20  grm.  citric  acid  in  900  c.c.  hot  water,  and, 
after  cooling,  diluting  the  solution  to  1000  c.c. 

The  albuminimeter-tube  is  filled  to  the  mark  U  with  urine, 
and  upon  this  the  picric  acid  solution  is  poured  until  the  level 
of  the  liquid  reaches  the  mark  R.  The  opening  of  the  tube  is 
closed  with  the  thumb,  and  the  liquids  are  mixed  by  inverting 
the  tube  several  times. 


114  NOTES  ON  CHEMICAL  LECTURES. 

The  tube  is  closed  with  a  rubber  stopper  and  stood  aside 
for  twenty-four  hours.  The  depth  of  the  sediment  is  ascer- 
tained by  observing  where  the  top  of  the  sediment  comes  in 
contact  with  a  line  on  the  scale. 

The  figures  on  the  scale  represent  the  number  of  grammes 
of  albumin  in  1000  c.c.  urine. 

* 

The  results  are  not  absolutely  accurate  because  of  the  pre- 
cipitation of  creatinine  by  picric  acid,  but  sufficiently  accurate 
for  clinical  purposes.  - 

QUALITATIVE  TESTS  FOR  BILIARY  COLORING  MATTER 
IN  URINE. 

1.  Urine  containing  biliary  coloring  matter  when  violently 
shaken   in   a  test-tube  yields   a   yellow  foam ;    normal  urine 
yields  a  white  foam. 

2.  The  urine  is  filtered  through  a  white  filter  paper.     The 
filter  paper  is  taken  from  the  funnel  and  unfolded  and  spread 
on   a  large  porcelain  dish  or  plate.     Slightly  yellow,  strong- 
nitric  acid  is  dropped  on  the  filter.     If  unaltered  biliary  color- 
ing matter  is  present,  concentric   rings  of  color  will  be  pro- 
duced where  the  drop  of  nitric  acid  comes  in  contact  with  the 
filter.     The  colors  from  the  centre  to  the  periphery  are  red, 
violet,  blue,  and  green.      Albumin  in  the  urine  interferes  with 
this  test.     It  may  be  removed  by  boiling  and  filtering.     Small 
quantities  of  biliary  coloring  matter  may  be  precipitated  with 
the  albumin   but  may  be    recovered  by  extracting  the  coag- 
ulated albumin  with  chloroform,  evaporating  the  solution  to 
dryness  in  a  porcelain  dish  and  applying  the  nitric  acid  test 
directly  to  the  residue. 

3.  The  urine  is  treated  with  a  few  drops  of  sodium  hydrox- 
ide, to  render  it  slightly  alkaline,  and  calcium  chloride  is  added 
in  excess.     The  precipitate  is  collected  on  a.  filter.     (The  pre- 
cipitate from  icteric  urine  is  yellow ;  from  normal  urine,  white.) 
When  all  of  the  liquid  has  passed  through,  the  filter  is  un- 
folded and  spread  on  a  large  porcelain  dish  or  plate  and  slightly 
yellow,  strong  nitric  acid  is  dropped  on  the  filter.     If  unaltered 
biliary  coloring  matter  is  present,  concentric  rings  of  color  will 
be  produced  where  the  drops  of  nitric  acid  come  in   contact 


^ 


i(*^J&l~CX^4 
(^     fa 


NOTES  ON  CHEMICAL  LECTURES.  115 

with  the  filter.     The  colors  from  centre  to  periphery  are  red, 
violet,  blue,  and 


Acetone,  CjHgO.  Defection  in  urine  :  About  600  c.c.  of 
urine  are  acidulated  with  acetic  acid  (about  2  c.c.  of  acid 
to  every  100  c.c.  of  urine),  and  distilled  until  about  50  c.c. 
of  distillate  are  collected  in  the  receiver.  To  this  distillate  a 
few  drops  of  a  dilute  solution  of  sodium  hydroxide  are  added 
and  then  a  slight  excess  of  concentrated  solution  of  iodo- 
potassium  iodide  (iodine  dissolved  in  potassium  iodide  solu- 
tion) is  added.  In  the  presence  of  acetone,  the  solution,  after 
the  lapse  of  a  little  time,  becomes  slightly  yellow  in  color  and, 
after  standing  some  time  longer,  a  yellow,  crystalline  pre- 
cipitate of  iodoform,  which  may  be  recognized  by  its  peculiar 
odor,  appears. 

Diacetic  acid,  C4H0O3.  Detection  in  urine  :  Urine  con- 
taining an  appreciable  quantity  of  diacetic  acid  when  treated  \  .- 
with  a  solution  of  ferric  chloride  becomes  claret  red  in  color. 
The  substances  which  appear  in  the  urine  after  the  ingestion 
of  antipyrin,  kairin,  and  thallin  also  produce  a  claret-red  color 
with  ferric  chloride. 


TOXICOLOGY. 


A  poison  is  any  substance  which,  when  taken  into  the 
body  and  either  being  absorbed  or  by  its  direct  chemical  action 
upon  the  parts  with  which  in  contact,  or  when  applied  externally 
and  entering  the  circulation,  is  capable  of  producing  deleterious 
effects. 

Poisons   vary  greatly  in  regard  to  their  toxic  action. 

Thus,  aconitinc,  one  of  the  most  active  poisons,  has  proved 
fatal  to  an  adult  in  the  dose  of  -fa  grain.  The  activity  of 
aconitinc  is  about  seven  times  greater  than  that  of  strychnine, 
and  about  forty  times  greater  than  that  of  arsenic.  The  activity 
of  poisons  may  be  expressed  by  their  fatal  toxic  action  per 
kilogramme  of  body  weight  as  follows  : 

ti.  Aconitine,  0.056  mgrm.  per  kilo.,  or  about  1  to  18,000,000 
parts  of  body  weight. 

15 


116  NOTES  ON  CHEMICAL  LECTURES. 

b.  Strychnine,  0.400  mgrm.  per  kilo.,  or  about  1  to  2,500,000 

parts  of  body  weight. 

c.  Arsenic,  2.24  mgrm.  per  kilo.,  or  about  1  to  500,000  parts 

of  body  weight. 

CAUSES  WHICH  MODIFY  THE  EFFECTS  OF  POISONS. 

a.  Idiosyncrasy,    or    a    peculiarity   of    constitution,   may 
variously  modify  the  effects  of  poisons. 

b.  Habit   may  render    certain    poisons    harmless    in   doses 
which  to  most  persons  would  prove  rapidly  fatal. 

c.  Disease  :   In  certain  diseased  conditions  of  the  system 
there  is   a   diminished   susceptibility  to   the  action  of  certain 
poisons,  whilst  in  others  there  is  an  increased  susceptibility, 
even  to  the  action  of  the  same  substance. 

d.  Condition  of  the  stomach :    The  presence  of  another 
substance  or  poison  ;  sleep. 

CLASSIFICATION  OF  POISONS. 

a.  Irritant    poisons,   as    a    class,    produce    irritation    and 
inflammation  of  the  stomach  and  bowels,  attended  or  followed 
by  intense  pain  in  these  parts,  tenderness  of  the  abdomen,  and 
violent  vomiting  and  purging,  the  matters  evacuated  being 
often  tinged  with  blood. 

The  irritant  poisons  may  be  divided  into  three  sections, — 
namely,  mineral,  vegetable,  and  animal. 

b.  Narcotic    or    cerebral  poisons  are  such  as  act   prin- 
cipally on  the  brain  and  spinal  marrow,  more  especially  on  the 
former. 

c.  Narcotico-irritants  partake,  as  indicated  by  their  name, 
of  the  action  of  both  the  preceding  classes. 

SOURCES  OF  EVIDENCE  OF  POISONING. 

1.  Evidence  from  symptoms. 

a.  The  symptoms  occur  suddenly,  and  soon  after  the  taking 
of  some  solid  or  liquid. 

b.  The  symptoms  rapidly  run  their  course. 


.  uro 


77;  "      -III  a^ 


^ 


•»-•*. 


1 


NOTES  ON  CHEMICAL  LECTURES.  117 

2.  Evidence  from  post-mortem  appearances. 

a.  The  irritant  poisons,  as  a  class,  usually  produce  irritation 
and  inflammation  of  one  or  more  portions  of  the  alimentary 
canal,  the  effects  being   sometimes  confined  to  the  stomach, 
while  at  other  times  they  extend  to  a  greater  or  less  degree 
throughout  the  entire  canal. 

b.  Narcotic  poisons,  in  some  instances,  produce  more  or  less 
distension  of  the  veins  of  the  brain,  but  in  others  they  leave 
no  marked  morbid  appearances,  and  in  none  are  the  appear- 
ances peculiar.  ^ 

c.  Narcotico-irritants  partake,  in  the  nature  of  their  effects, 
of  both  the  preceding  classes. 

APPEARANCES  COMMON  TO  POISONING  AND  DISEASE. 

a.  Redness  of  the  stomach  and  intestines  as  the  effect  of 
poisoning  cannot  in  itself  be  distinguished  from  that  arising 
from  natural  disease. 

b.  Softening  of  the  stomach  is  another  appearance  which 
may  give  rise  to  embarrassment.     When  due  to  the  action  of 
poison,  it  is  usually  accompanied  by  other  appearances  which 
readily  distinguish  it  from  the  effects  of  ordinary  disease  or 
post-mortem  changes. 

c.  Ulceration  and  perforation  of  the  stomach  are  not  un- 
frequently  produced  by  corrosive  poisons,  but  they,  especially 
the  latter,  are  rarely  met  with  as  the  result  of  the  action  of 
the  simple  irritants.     As  the  effect  of  natural  disease  or  post- 
mortem action  they  are  not  uncommon. 

d.  Points  to  be  observed  in  post-mortem  examinations  : 
All  investigations  of  this  kind  should  be  made  in  the  presence 
of  the  proper  law  officer ;  and  it  is  well  for  the  examiner  to 
have  the  assistance  and  corroboration  of  another  physician. 
All   appearances    observed,  whether  abnormal   or  otherwise, 
should  be  fully  written  down  at  the  time  of  their  observance. 

All  the  organs  and  blood  removed  for  the  purpose  of  examina- 
tion should  be  collected  in  separate,  new,  clean  glass  vessels, 
great  care  being  taken  tJiat  none  of  the  reserved  substances  at  any 
time  be  brought  in  contact  with  any  substance  that  afterwards 
might  give  rise  to  suspicion.  Before  passing  out  of  the  sight 


118  NOTES  ON  CHEMICAL  LECTURES. 

of  the  examiner,  the  bottles  should  be  securely  sealed  and  fully 
labeled.  They  should  then  be  retained  in  /iis  sole  possession 
until  delivered  to  the  proper  legal  official. 

3.  Evidence  from  chemical  analysis. 

a.  In  most  charges  of   poisoning  the   final  issue  depends 
upon  the  results  of  the  chemical  analysis.     In  fact,  in  many 
instances  in  which  the  evidence  from  symptoms,  post-mortem 
appearances,  and  moral  circumstances  is  very  equivocal  or  in 
part  wanting,  a  chemical  examination  may  at  once  determine 
the  true  cause  of  death..    It  must  be  remembered,  however,  a 
person  may  die  from  the  effects  of  poison  and  not  a  trace  of 
its  presence  be  discoverable  in  any  part  of  the  body  ;  while,  on 
the  other  hand,  the  mere  discovery  of  a  poison  in  the  food  or 
drink  taken,  or  in  the  body  after  death,  is  not  in  itself  positive 
proof  that  it  occasioned  death. 

b.  Substances  requiring  analysis :    The  substances  that 
may  directly  become  the  subject  of  a  chemical  analysis  in  a 
case  of  suspected  poisoning  are :  the  pure  poison  in  its  solid 
or  liquid  state ;  suspected  articles  of  food  or  medicine  ;  matters 
ejected   from   the  body  by  vomiting  or  purging ;   the  urine  ; 
suspected  solids  found  in  the  stomach  or  intestines  after  death  ; 
the  contents  of  the  stomach  or  bowels ;  any  of  the  soft  organs 
of  the  body,  as  the  liver,  spleen,  etc.,  and  the  blood. 

There  are  some  poisons  for  which  no  definite  chemical  test 
is  known. 

Some  poisons  are  detected  by  a  combination  of  tests,  and 
others  by  a  single  test  or  tests. 

4.  Limit  of  tests. 

1  part  of  arsenic  may  be  detected  in  5,000,000  parts  water. 
Strychnine,  -^fam  of  a  grain. 
Hydrocyanic  acid,  ronVrU"  °^  a  gram- 

5.  Limit  of  recovery. 

6.  Failure  to  detect  a  poison. 

Numerous  instances  of  poisoning  are  reported  in  which 
persons  died  from  the  effects  of  poison  and  none  was  dis- 
covered by  chemical  analysis  in  the  body  after  death.  This 
result  has  most  frequently  been  observed  in  poisoning  with 
organic  substances,  but  it  has  happened  when  mineral  poisons, 


la^^^x/v-T.     ^ 


NOTES  ON  CHEMICAL  LECTURES.  119 

and  even  those  which  are  most  easily  detected  by  chemical 
tests,  had  been  taken  in  large  quantity. 

A  failure  of  this  kind  may  be  due  to  any  of  the  following 
circumstances:  1.  The  poison  may  have  been  one  of  the 
organic  poisons,  which  cannot  at  present  be  recognized  by 
chemical  tests.  2.  The  quantity  present  in  the  part  examined 
may  have  been  so  minute  as  under  the  circumstances  not  to 
admit  of  recovery,  or  at  least  in  a  state  sufficiently  pure  to 
permit  its  true  nature  to  be  established:  3.  The  poison  may 
have  been  removed  from  the  stomach  and  intestines  by  vomit- 
ing and  purging  or  by  absorption.  4.  The  absorbed  poison 
may  have  been  carried  out  of  the  system  with  the  excretions. 
5.  If  volatile,  like  hydrocyanic  acid  and  some  few  other  poisons, 
it  may  have  been  dissipated  in  the  form  of  vapor.  6.  It  may 
have  undergone  a  chemical  change  in  the  living  body,  or, 
especially  if  of  organic  origin,  have  decomposed  in  the  dead 
body  if  far  advanced  in  putrefaction. 

7.  Caution  regarding  the  purity  of  reagents. 

8.  Preservation  of  chemical  results  and  material. 

9.  Duties  and  rights  of  experts. 

An  expert  can  not  be  compelled  to  make  a  post-mortem 
examination  or  chemical  analysis. 

Having  made  the  examination,  the  knowledge  acquired  is 
common  property,  J=d(«  ~i~~-~--r- 4**.  X>J(^{  A^"  t^-^-C--/., 

The  expert  should  be  cautious  in  expressing  opinions  before 
the  case  is  called  for  trial. 

ARSENICUM. 

Atomic  weight,  75. 

In  its  pure  state  arsenicum  has  a  steel-gray  color,  a  bright 
metallic  lustre,  and  has  a  crystalline  structure.  In  dry  air  it 
remains  unchanged,  but  in  the  presence  of  moisture  it  slowly 
absorbs  oxygen  and  assumes  a  dark-gray  appearance.  It 
volatilizes  at  a  temperature  of  110°  C.  (230°  F.). 

Metallic  arsenic,  when  taken  into  the  stomach,  is  capable  of 
acting  as  a  powerful  poison,  but  perhaps  only  in  so  far  as  the 
metal  becomes  oxidized  and  converted  into  arsenious  acid. 


120  NOTES  ON  CHEMICAL  LECTURES. 

Compounds  of  arsenicum  and  oxygen  : 

As2O3,  arsenious  oxide,  molecular  weight,  198. 
As2O5,  arsenic          "  "  "        230. 

Both  form  acids  with  the  elements  of  water : 

As2O3  +  3H2O  =  2H3AsO3,  arsenious  acid. 
As2O5  -f  3H2O  =  2H3AsO4,  arsenic  acid. 

Arsenious  oxide  (As2O3)  is  readily  obtained  by  volatilizing 
metallic  arsenicum  in  a  free  supply  of  air. 

It  is  found  in  commerce  either  as  a  white  or  dull  white, 
opaque  powder,  or  in  the  form  of  large,  hard  masses. 

Symptoms  of  poisoning  with  As2O3 :  These  are  subject 
to  great  variation.  Sooner  or  later  after  a  large  dose  of  the 
poison  has  been  swallowed  there  is  usually  a  sense  of  heat 
and  constriction  in  the  throat,  with  thirst,  nausea,  and  burn- 
ing pain  in  the  stomach.  The  pain  becomes  excruciating, 
and  is  attended  with  violent  vomiting  and  retching ;  the 
matters  vomited  present  various  appearances,  being  some- 
times streaked  with  blood,  and  at  other  times  of  a  bilious 
character;  the  pain  in  the  stomach  is  increased  by  pressure. 
As  the  case  progresses  the  pain  extends  throughout  the  ab- 
domen, and  there  is  generally  severe  purging  and  tenesmus  ; 
the  matters  passed  from  the  bowels  not  unfrequently  contain 
blood.  The  thirst  usually  becomes  very  intense ;  in  some 
instances  there  is  great  difficulty  in  swallowing.  The  features 
are  collapsed  and  expressive  of  great  anxiety ;  the  pulse  is 
quick,  small,  and  irregular ;  the  eyes  red  ;  the  tongue  dry  and 
furred ;  the  skin  cold  and  clammy,  but  sometimes  hot ;  the 
respiration  difficult ;  and  sometimes  there  are  violent  cramps 
of  the  legs  and  arms.  The  urine  is  frequently  diminished  in 
quantity  and  its  passage  attended  with  great  pain.  Stupor, 
delirium,  paralysis,  and  convulsions  have  also  been  observed. 
In  many  cases  death  takes  place  calmly,  and  the  intellectual 
faculties  remain  clear  to  the  last. 

Fatal  quantity  :  2  grains  taken  in  divided  doses  during  a 
period  of  five  days  have  proved  fatal.  On  the  other  hand, 
2  ounces  have  been  ingested  and  recovery  occurred  in  six 
hours. 


NOTES  ON  CHEMICAL  LECTURES.  121 

When  fatal :  Usually  in  twelve  to  twenty-four  hours, 
although  in  three  cases  death  occurred  in  two  hours,  and  in 
one  case  in  twenty  minutes. 

Antidote :  Hydrated  ferric  oxide  (ferric  hydroxide)  is  the 
most  important  chemical  antidote. 

The  antidotal  action  of  this  substance  is  due  to  its  forming 
an  insoluble  compound,  ferric  arsenate,  with  the  arsenious 
oxide. 

Thus, 

2Fe2O33H2O  -f  2H3AsO3  =  Fe32AsO4  -f  FeO  +  9H2O  - 

The  antidote  should  be  given  in  its  moist  state  and  administered 
in  large  excess.  The  antidote  has  no  action  on  arsenious  oxide 
in  its  solid  state,  but  only  when  in  solution. 

Hydrated  ferric  oxide  (ferric  hydroxide)  may  readily  be 
prepared  by  treating  ordinary  tincture  of  ferric  chloride  with 
slight  excess  of  ammonia,  collecting  the  precipitate  on  a 
muslin  strainer,  and  washing  it  with  water  until  it  no  longer 
emits  the  odor  of  ammonia.  A  tablespoonful  or  more  of  the 
moist  magma,  mixed  with  a  little  water,  may  be  given  at  a 
dose.  The  antidote  should  always  be  freshly  prepared. 

The  ordinary  magnesia  of  the  shops  may  be  used  to  add  to 
the  tincture  of  ferric  chloride  instead  of  ammonia,  and  the 
mixture  containing  excess  of  magnesia  and  hydrated  ferric 
oxide  may  be  administered  at  once  without  filtering. 

Antiseptic  properties  of  arsenic  :  The  preservative  power 
of  arsenic  when  brought  in  direct  contact  with  animal 
textures  is  well  known  :  and  the  poison  seems  to  exert  a 
similar  action  when  carried  by  means  of  the  circulation  to 
the  different  tissues  of  the  body.  The  bodies,  therefore,  of 
those  who  have  died  from  the  effects  of  this  poison  are  not 
unfrequently  found  in  a  good  state  of  preservation,  even  long 
periods  after  death. 

Solid  arsenious  oxide.     Tests. 

a.  It  is  volatile  at  a  temperature  of  138°  C.  (280°  F.). 

b.  When  heated  on   charcoal  in    the   reducing  flame  it  is 
dissipated  in  the  form  of  white  fumes,  and  emits  a  garlic-like 
odor. 


122  NOTES  ON  CHEMICAL  LECTURES. 

|  c.  When  heated  in  a  reduction-tube,  arsenious  oxide  vola- 
tilizes without  fusing,  and  recondenses  in  the  cooler  portion  of 
I  the  tube  in  the  form  of  minute,  octahedral  crystals. 

d.  When  heated  in   a    reduction-tube  containing   a    small 

I  piece   of  ignited   charcoal,  the  arsenious  oxide  is  volatilized 

\  and  deoxidized  in  its  passage  over  the  ignited  charcoal,  and 

1  deposits  in  the  cooler  portion  of  the  tube  as  a  sublimate  of 

Imetallic  arsenic. 

A  similar  reaction  occurs  when  arsenious  oxide  is  heated  in 
la  tube  with  a  perfectly  dry  mixture  of  powdered  charcoal  and 
podium  carbonate. 

If  the  closed  end  of  the  tube  be  removed  (by  breaking  it 
off)  and  the  metallic  sublimate  then  heated,  it  is  readily  vola- 
tilized and  oxidized  into  arsenious  oxide,  which  condenses  in 
octahedral  crystals. 

The  metallic  sublimate  is  soluble  in  a  solution  of  either 
sodium  or  calcium  hypochlorite. 

-  c.  When  arsenious  oxide  is  heated  in  a  reduction-tube  with 
a  perfectly  dry  mixture  of  about  equal  parts  sodium  carbonate 
and  potassium  cyanide,  reduction  will  take  place  and  a  sub- 
limate of  metallic  arsenic  will  form  in  the  cooler  portion  of 
^he  tube. 

f.  Potassium  ferrocyanide  may  be  employed  as  a  reducing 
agent  instead  of  potassium  cyanide.     The  arsenious  oxide  is 
mixed  with  about  6  or  8  times  its  volume  of  dry  potassium 
ferrocyanide,  and  heated  in  a  tube  as  in  the  preceding  test. 
Solutions  of  arsenious  oxide.     Tests. 

a.  Ammonio-silver  nitrate  test :  Ammpnio-silver  nitrate 
throws  down  from  aqueous  solutions  of  arsenious  acid  a  bright- 
yellow  precipitate  of  tribasic   silver  arsenite  (Ag3AsO3),  the 
reaction  being,  perhaps, 

2H3AsO3  +  6AgNH3NO3  =  2Ag3AsO3  +  6NH4NO3 

The  precipitate  is  readily  soluble,  forming  a  colorless  solu- 
tion, in  ammonium  hydroxide  and  in  nitric  and  acetic  acids, 
sparingly  soluble  in  ammonium  nitrate,  and  insoluble  in  the 
fixed  caustic  alkalies. 

b.  Ammonio-copper    sulphate    test :      Ammonio-copper 
sulphate  produces   in    solutions  of  arsenious  acid   a    green, 


7. 


NOTES  ON  CHEMICAL  LECTURES.  123 

amorphous  precipitate  of  copper  arsenite  (CuHAsO3),  known 
also  as  Scheele's  green,  the  reaction  being,  perhaps, 

2H3AsO3  +  2CuH2O2(NH3)2,  (NH4)2SO4  =  2CuHAsO3  + 
2(NH4)2S04  +  4NH4OH 

The  precipitate  is  nearly  insoluble  even  in  large  excess  of 
the  precipitant,  but  readily  soluble  in  ammonia  and  in  free 
acids.  From  very  dilute  solutions  of  the  poison  the  precipitate 
does  not  appear  of  its  characteristic  color  until  the  mixture 
has  stood  some  time.  The  same  precipitate  is  thrown  down, 
from  solutions  of  neutral  arsenites  by  copper  sulphate  alone. 

c.  Hydrogen  sulphide   test :    Hydrogen  sulphide  throws 
down  from  solutions  of  arsenious  acid,  previously  acidulated 
with  hydrochloric  acid,  a  bright-yellow,  amorphous  precipitate 
of  arsenious  sulphide  (As2S3),  the  reaction  being 

2H3AsO3  +  3H2S  j==  As2S3  +  6H2O 

d.  Reinsch's  test ;  When  a  solution  of  free  arsenious  acid 
or  an  arsenite  is   strongly  acidulated  with  hydrochloric  acid, 
and  the  mixture  boiled  with  a  slip  of  bright  metallic  copper, 
the  latter  decomposes  the  arsenical  compound  and  receives  a 
coating  of  metallic  arsenic,  or  an  alloy  of  copper  and  arsenic 
(As2Cu5).     The  arsenical  nature  of  the  deposit  may  be  shown 
in  the  following  manner :  the  coated  copper,  after  having  been 
carefully  washed  with  pure  water  and  dried  in  a  water-oven, 
is  heated   by  means  of  a  spirit  lamp  or  the  small  flame  of  a 
Bunsen  burner,  in  a  narrow  and  perfectly  dry  and  clean  reduc- 
tion-tube, when  the  arsenic  volatilizes,  and,  becoming  oxidized, 
yields  a   sublimate  of  octahedral  crystals  of  arsenious  oxide. 
This  sublimate  usually  forms  within  from  a  quarter  to  half  an 
inch  above  the  .point  at  which  the  heat  is  applied.     When  the 
sublimate  is  not  exceedingly  minute,  it  presents  a  well-defined 
ring  of  sparkling  crystals  to  the  naked  eye. 

c.  Marsh's  test :  When  metallic  zinc  is  treated  with  diluted 
sulphuric  acid,  the  hydrogen  of  the  latter  is  displaced  by  the 
metal  with  the  formation  of  zinc  sulphate,  the  hydrogen  dis- 
placed passing  off  in  its  free  state  : 

Zn  +  H2SO4  =  ZnSO4  +  H2 

16 


124  NOTES  ON  CHEMICAL  LECTURES. 

If,  however,  arsenious  acid  or  arsenic  acid,  or  any  of  the 
soluble  compounds  of  the  metal,  be  present,  the  nascent 
hydrogen  decomposes  the  arsenical  compound,  and,  uniting 
with  the  metal,  forms  arsenuretted  hydrogen  gas  (AsH3), 
which  is  evolved  in  its  free  state. 

The  reaction  in  the  case  of  arsenious  acid  is  as  follows : 

3Zn  +  3H,SO4  -f-  H3AsO3  =  3ZnSO4  +  4H2O  +  AsH3 

Metallic  zinc  is  placed  in  the  flask  of  the  apparatus  and 
a  quantity  of  a  cooled  mixture  of  1  volume  of  pure  concen- 
trated sulphuric  acid  and  4  volumes  of  distilled  water,  suffi- 
cient to  cover  the  zinc,  is  poured  in  through  a  funnel  tube  and 
the  decomposition  of  the  acid  allowed  to  proceed.  If  the  zinc 
should  act  very  slowly  upon  the  acid,  as  is  frequently  the  case 
with  the  pure  metal,  the  action  may  be  hastened  by  the  addi- 
tion of  a  few  drops  of  platinic  chloride. 

Should  the  zinc  or  sulphuric  acid  be  contaminated  with 
arsenic  this  will  give  rise  to  arsenuretted  hydrogen.  There- 
fore, before  applying  the  test  to  a  suspected  solution,  the  purity 
of  the  materials  must  be  fully  established.  For  this  purpose, 
after  the  apparatus  has  become  completely  filled  with  hydrogen 
and  while  the  gas  is  still  being,  evolved,  the  outer  uncontracted 
portion  of  the  reduction-tube  is  heated  to  redness  for  about 
fifteen  minutes  or  longer.  If  this  fails  to  produce  a  metallic 
deposit  or  stain  in  the  contracted  part  of  the  tube,  in  advance 
of  the  part  heated,  the  material  may  be  considered  free  from 
arsenic.  The  purity  of  the  materials  having  been  thus  estab- 
lished, it  may  be  necessary  to  wash  and  renew  the  zinc,  dry 
the  tubes,  and  add  a  fresh  portion  of  the  diluted  acid. 

The  apparatus  being  adjusted  and  completely  filled  with 
evolved  hydrogen,  the  jet  of  gas,  as  it  issues  from  the  drawn- 
out  end  of  the  reduction-tube,  is  ignited,  care  being  taken  not 
to  apply  a  light  until  the  whole  of  the  atmospheric  air  is 
expelled  from  the  apparatus,  as  otherwise  an  explosion  might 
occur.  A  small  quantity  of  the  arsenical  solution  is  then 
introduced  into  the  funnel-tube  and  washed  into  the  flask  by 
the  subsequent  addition  of  a  few  drops  of  the  diluted  sulphuric 
acid.  The  decomposition  of  the  arsenical  compound,  with 
the  evolution  of  arsenuretted  hydrogen,  will  commence 


•£j2yr"v 


LC^V^- 

<*l 


NOTES  ON  CHEMICAL  LECTURES.  125 

immediately.     The  presence  of  the  arsenuretted  gas  may  be 
established  by  three  different  methods, — namely, 

a.  By  the  properties  of  the  ignited  jet. 

b.  By  decomposing  it  by  heat  applied  to  the  reduction-tube. 

c.  By  its  action  upon  a  solution  of  argentic  nitrate. 

a.  The   ignited  jet ;  As  soon  as  the  arsenical  solution  is 
introduced  into  the  flask  the  evolution  of  gas  increases.     The 
flame  of  the  jet  will  now  increase  in  size,  acquire  a  bluish  tint, 
and,  unless  only  a  minute  quantity  of  arsenic  is  present,  evolve 
white  fumes  of  arsenious  oxide ;  so,  also,  the  flame  sometimes 
emits  a  peculiar  garlic- like  odor.     If  the  white  fumes  be  re- 
ceived upon  a  cold  surface  they  condense  to  a  white  powder, 
which  sometimes  contains  octahedral  crystals.     This  is   not  a 
delicate  method  for  detecting  the  presence  of  arsenic,  and 
should  never  be  employed  to  the  exclusion  of  the  following 
modification,  viz. : 

If  the  flame  be  allowed  to  strike  against  a  cold  body,  as  a 
piece  of  white  porcelain,  it  yields  a  brown  to  black  deposit  of 
metallic  arsenic. 

Fallacy ;  Solutions  of  antimony,  under  these  same  condi- 
tions undergo  decomposition  with  -the  production  of  anti- 
monuretted  hydrogen,  which,  like  arsenuretted  hydrogen, 
burns  with  the  evolution  of  white  fumes,  and  yields  metallic 
deposits  upon  cold  surfaces  applied  to  the  flame.  The  spots 
produced  by  arsenic  are  readily  soluble  in  a  solution  of  either 
sodium  or  calcium  hypochlorite,  whereas  those  from  antimony 
are  insoluble,  or  dissolve  only  after  prolonged  digestion  in  the 
hypochlorite  solution. 

b.  Decomposition  of  the  gas  by  heat :  When  arsenuretted 
hydrogen,  as  evolved  in   Marsh's  test,  comes  in  contact  with 
the   red-hot   portion  of  the  reduction-tube,  it  is  decomposed 
with  the  production   of  a  deposit  of  metallic  arsenic  in  the 
contracted  part  of  the  tube,  in  advance  of  the  flame. 

Fallacy :  Antimonuretted  hydrogen  also  is  decomposed 
under  the  above  conditions  with  the  deposition  of  metallic 
antimony.  Antimony,  however,  is  almost  wholly  deposited 
before  reaching  the  part  of  the  reduction-tube  to  which  the 
flame  is  applied ;  when  it  yields  deposits  on  both  sides  of  the 


126  NOTES  ON  CHEMICAL  LECTURES. 

flame,  the  outer  one  is  quite  near  the  flame.  On  the  other 
hand,  arsenic  deposits  about  one-half  to  three-quarters  of  an 
inch  in  advance,  or  on  the  outer  side  of  the  flame,  and  never 
before  reaching  the  part  of  the  tube  to  which  the  heat  is 
directly  applied. 

c.  Decomposition  by  argentic  nitrate  ;  If  the  reduction- 
tube  of  the  apparatus  be  substituted  by  a  tube  bent  at  a  right 
angle,  and  the  arsenuretted  hydrogen  conducted  into  a  solu- 
tion of  argentic  nitrate,  both  the  gas  and  the  silver  salt  undergo 
decomposition  with  the  production  of  arsenious  acid,  which 
remains  in  solution,  and  the  separation  of  metallic  silver,  which 
falls  as  a  black  precipitate.  The  reaction  is 

AsH3  +  6AgNO3  +  3H2O  =  6Ag  +  H3AsO3  +  6HNO3 

The  presence  of  arsenious  acid  in  the  solution  may  be  shown 
by  the  usual  tests  for  that  substance. 

SEPARATION  OF  ARSENIC  FROM  ORGANIC  TISSUES. 

/  Disintegrate  the  organic  matter  by  means  of  hydrochloric 
cid  and  potassium  chlorate,  under  the  action  of  heat. 

The  following  proportions  of  tissue,  acid,  and  the  chlorate 
yield  very  satisfactory  results  : 

Treat  300  grm.,  or  10  ounces,  of  the  solid  tissue,  as  of  the 
iver,  cut  into  very  small  pieces  and  placed  in  a  clean  porcelain 
dish,  with  a  mixture  of  60  c.c.,  or  2  fluid  ounces,  of  strong 
lydrochloric  acid  and  240  c.c.,  or  8  fluid  ounces,  of  water. 

Heat  the  mixture  on  a  sand-bath,  and  when  at  about  the 
Doiling  temperature,  add  about  1  grm.,  or  15  grains,  of  pow- 
dered potassium  chlorate,  and  repeat  the  addition  at  intervals 
of  a  few  minutes,  with  frequent  stirring,  until  about  6  or  7 
rm.,  or  100  grains,  have  been  added  and  the  mass  has  become 
homogeneous  and  of  a  light-yellow  color.  During  this  process 
water  should  occasionally  be  added  to  replace  that  lost  by 
evaporation. 

The  disintegrating  action  of  this  mixture  is  chiefly  due  to 
the  free  chlorine  and  chlorine  peroxide  evolved  by  the  mutual 
iecomposition  of  the  chlorate  and  a  portion  of  the  hydro- 
chloric acid. 

12HC1  =  4KC1  +  6H2O  +  3C1O2  -f  C19 


NOTES  ON  CHEMICAL  LECTURES.  127 

Moderately  heat  the  disintegrated  mass  until  the  odor  of 
chlorine  has  entirely  disappeared,  and  then  allow  to  cool. 
Transfer  the  cooled  mixture  to  a  moistened  linen  strainer, 
and,  when  the  liquid  has  all  passed,  wash  the  solids  with  a 
little  warm  water,  the  washings  being  collected  separately. 
Concentrate  the  washings  on  a  water-bath  to  a  small  volume, 
allow  to  cool,  then  add  the  washings  to  the  first  strained 
liquid,  and  filter  the  mixed  liquid  through  paper.  Any  arsenic 
present  will  now  exist  as  arsenic  acid. 

From  the  filtrate  thus  obtained  free  chlorine  must  be  com- 
pletely expelled,  otherwise  in  the  subsequent  treatment  of 
the  solution  with  sulphurous  acid  the  latter  will  be  acted  upon 
by  the  free  chlorine  resulting  in  the  formation  of  hydrochloric 
and  sulphuric  acids  and,  consequently,  the  sulphurous  acid 
would  have  no  action  upon  the  arsenic  acid  until  all  the  free 
chlorine  was  satisfied. 

SO2  -f  C12  -f  2H2O  =  2HC1  -f  H2SO4 

To  the  liquid  free  from  uncombined  chlorine  add  a  solution 
of  sulphurous  acid  until  it  smells  strongly  of  the  gas  (sul- 
phurous anhydride).  Any  arsenic  acid  present  will  be  reduced 
to  arsenious  acid,  in  which  form  the  metal  is  more  rapidly  and 
more  completely  precipitated  by  hydrogen  sulphide  than  when 
it  exists  in  the  form  of  arsenic  acid.  The  reducing  action  of 
the  gas  may  be  represented, 

H3AsO4  +  SO2  -f  H2O  =  H2SO4  -f  H3AsO3 

Concentrate  the  liquid  on  a  water-bath  to  a  volume  twice  that 
of  the  hydrochloric  acid  employed  in  preparing  the  mixture. 
In  this  concentrating  of  the  liquid  the  sulphurous  acid  must 
be  completely  expelled,  otherwise  in  the  subsequent  addition 
of  hydrogen  sulphide  decomposition  of  both  compounds 
occurs  with  the  formation  of  pentathionic  acid  and  separation 
of  sulphur. 

5SO2  H-  5H2S  =  4H2O  +  H2S5O6  -f  S5 

Allow  the  concentrated  liquid  to  cool,  and  then  filter. 

Pass  a  slow  stream  of  washed  hydrogen  sulphide  through 
the  filtrate  for  several  hours ;  then  gently  warm  it,  and  allow 
to  stand  twelve  to  twenty-four  hours.  Any  arsenic  present 


12S  NOTES  ON  CHEMICAL  LECTURES. 

will  be  precipitated  as  arsenious  sulphide  (As,S3),  together  with 
more  or  less  organic  matter  and  free  sulphur.  Should  the 
liquid  contain  mercury,  antimony,  copper,  or  lead,  these  metals 
would  also  be  precipitated  as  sulphides  by  the  hydrogen  sul- 
phide. Liquids  prepared  as  the  above  may  yield  with  hydrogen 
sulphide  a  brownish  or  yellowish  precipitate  of  organic  matter 
and  free  sulphur,  even  in  the  absence  of  any  metal. 

Collect  the  precipitate  on  a  small  filter  and  wash,  at  first 
with  water  containing  a  little  hydrogen  sulphide,  until  the 
washings  no  longer  contain  chlorine  (test  with  argentic 
nitrate). 

Dissolve  the  moist  precipitate  on  the  filter  with  dilute  am- 
monium hydroxide  (1  to  10),  which  will  dissolve  any  arsenious 
sulphide  present,  with  more  or  less  of  the  organic  matter  and 
free  sulphur.  The  sulphides  of  mercury,  antimony,  copper, 
and  lead  which  might  be  present  would  remain  undissolved, 
except  perhaps  a  slight  trace  of  the  antimony  sulphide. 

Collect  the  ammoniacal  liquid,  usually  of  a  dark -brown  color, 
in  a  small  porcelain  dish  and  evaporate  to  dryness  on  a  water- 
bath,  treat  the  residue  with  a  small  quantity  of  strong  nitric 
acid,  and  again  evaporate  the  liquid  to  dryness ;  repeat  the 
operation  with  nitric  acid,  if  necessary,  until  the  moist  residue 
has  a  yellow  color. 

Moisten  the  residue  with  a  few  drops  of  concentrated  solu- 
tion of  sodium  hydroxide  and  evaporate  to  dryness.  Treat 
the  residue  with  several  drops  of  concentrated  sulphuric  acid, 
and  heat  the  mass  on  a  sand-bath  until  it  becomes  about  dry  ; 
again  treat  the  residue  with  sulphuric  acid  and  heat  in  the 
same  manner  until  fumes  of  the  acid  are  no  longer  evolved. 

Pulverize,  if  necessary,  the  carbonaceous  residue,  and  boil 
it  with  a  small  quantity  of  water  containing  a  drop  or  two  of 
sulphuric  acid,  cool  the  liquid,  filter  off,  and  wash  the  insoluble 
carbonaceous  residue.  If  in  the  carbonization  the  whole  of 
the  free  sulphuric  acid  was  expelled,  the  resulting  solution 
(filtrate)  will  be  colorless  and  entirely  free  from  organic  matter. 
Add  1  or  2  c.c.  of  solution  of  SO2  to  reduce  As2O5  to  As2O3, 
and  then  heat  until  all  the  SO2  has  been  expelled.  Concen- 
trate the  solution  to  a  small  and  definite  volume  (say  20  c.c.), 
and  divide  it  into  two  equal  portions.  Make  the  qualitative 


O        - 
vf    Qs    is    fj    C^A^VVO      ^UtL^(      O*-  ^JUU( 

V 

/3 


NOTES  ON  CHEMICAL  LECTURES.  129 

tests  with  one  portion  and  the  quantitative  determination  with 
the  other  portion. 

With  the  first  portion 

a.  Apply  Reinsch's  test. 

b.  Marsh's       " 

With  the  second  portion  of  10  c.c.  make  the  quantitative 
determination. 

QUANTITATIVE  DETERMINATION. 

Acidulate  the  solution  with  a  few  drops  of  hydrochloric  acid, 
warm  to  about  blood-heat,  and  pass  a  stream  of  hydrogen  sul- 
phide through  the  liquid.  The  arsenic  will  be  precipitated  as 
arsenious  sulphide.  Collect  the  precipitate  on  an  equipoised 
or  on  a  weighed,  washed  filter,  wash  at  first  with  water  con- 
taining a  little  hydrogen  sulphide,  then  with  pure  water  until 
the  washings  are  free  from  chlorine.  Dry  the  precipitate  on 
the  filter  at  a  temperature  of  about  100°  C.,  and  weigh. 

The  quantity  of  As2O3  corresponding  to  the  weight  of  As2S3 
obtained  is  determined  by 

As2S:!.  As.2Os. 

246  :  198  ::  weight  of  precipitate  :  X  =  one-half, 
the  amount  of  arsenic  as  As2O3  recovered  from  the  quantity  of 
organic  tissue  employed. 

TESTS  FOR  SOME  OF  THE   MORE  COMMON  ORGANIC 
POISONS. 

Opium,. 

The  presence  of  opium  may  be  inferred  by  showing  the 
presence  of  meconic  acid,  an  organic  acid  peculiar  to  the  drug. 
For  this  purpose,  the  aqueous  extract  of  the  substance  is 
treated  with  lead  acetate,  which  will  precipitate  the  acid  as 
meconate  of  lead.  This  is  collected  on  a  filter  and  washed, 
the  filtrate  being  reserved  for  the  examination  for  morphine. 
The  contents  of  the  filter  are  diffused  in  a  small  quantity  of 
water,  and  the  lead  precipitated  by  H3S.  The  filtrate  from  this 
precipitate  is  concentrated  to  a  small  volume  and  treated  with 
a  drop  of  ferric  chloride  solution,  when,  if  meconic  acid  is 
present,  a  deep  blood-red  coloration  will  be  produced.  Limit  of 
reaction,  y^-jj^nj-  solution. 


130  NOTES  ON  CHEMICAL  LECTURES. 


I    Morphine.*  <a^-^ev:<Lj" 

tf.  Sulpho-molybdic  acid  (Froehde)  :  The  reagent  is  pre- 
pared by  heating  1  part  of  molybdic  acid  with  100  parts  of 
strong  H2SO4  C.  P.,  until  complete  solution  has  taken  place. 
On  the  addition  of  a  drop  of  the  reagent  to  morphine  or  any 
:>f  its  salts  in  the  solid  state,  on  a  porcelain  test  tablet,  a  purple 
ir  crimson  color  appears  immediately,  passing  through  various 
shades  and  finally  to  blue,  which  appears  first  at  the  margin  of 
he  mixture.  Limit,  YoVoTo  gram- 

b.  Neutral  ferric  chloride  added  to  morphine  or  any  of  its 
ialts  in  the  solid  state,  produces  a  deep  blue  color,  which  is 

discharged  by  acids,  alkalies  and  heat.     Limit,  ^o  JJ-QO"  grain- 

c.  lodic  acid  in  strong  solution,  added  to  morphine  or  any 
of  its  salts  in  the  solid  state,  the  acid  is  decomposed  with  the 
liberation  of  iodine,  forming  a  brown  or  reddish-brown  pre- 
cipitate.    Limit,  yoVg-  grain. 

The  presence  of  free  iodine  may  be  shown  by  agitating  the 
mixture  with  either,  carbon  disulphide  or  chloroform,  which 
will  dissolve  £he  iodine  and  assume  a  purple  color. 

Strychnine. 

a.  "  Color-test;  "  Strychnine  or  any  of  its  salts  dissolved 
in  a  drop  of  strong,  chemically  pure  H2SO4,  on  a  porcelain  . 

test  tablet,  and  a  minute  crystal  of  potassium  dichromatejBrawri  v 

through  the  solution  by  means  of  a  glass  rod,  immediately 
produces  a  cJiaracteristic  succession  of  colors  beginning  with 
blue,  passing  into  purple,  violet  and  greenish-yellow.  Limit, 


b.  The  caustic  alkalies  precipitate  the  free  alkaloid  from 
solutions  of  salts  of  strychnine  in  the  form  of  a  white  po\vder, 
which  soon  assumes  the  crystalline  form.     Limit,  ^^00  grain. 

To  prove  the  true  nature  of  the  precipitate  apply  the  color 
test. 

c.  Potassium  dichromate  produces  a  bright  yellow  pre- 
cipitate of  strychnine  chromate,  which  quickly  becomes  crys- 
talline.    Limit,  10000  gram- 

This  precipitate  treated  with   a  drop  of  strong,  chemically 
pure  H,SO4  alone  gives  the  color  reaction. 


' 


T^^         > 


jl   U-*-f-  W 


*/ 


Errata. — Page  24,  first  line,  read  acetic  instead  of  sulphuric. 


INDEX. 


PAGE  PAGE 

Acetic  acid 27  Reinsch's  test  for 123 

Acetone 115  separation  of,  from  organic  tissues  .    .  126 

tests  for 115  tests  for 121 

Albumin 108  Azotized  compounds 6 

biuret  test  for iia  Baryta  mixture,  composition  of 74 

boiling  test  for 109  Beckmann's  method 18 

Esbach's  method  for  quantitative  Benzoic  acid 86 

determination  of 113  Benzol,  empirical  formula  of ai 

Heller's  test  for no  graphic  formula  of 21 

native 108  molecular  formula  oi 21 

picric  acid  test  for in  ring • 21 

potassium  ferrocyanide  test  for     .    .    .  in  Bile,  tests  for 114 

qualitative  tests  for 109  Biuret 65 

quantitative  determination  oi     ....  113  test 112 

trichloracetic  acid  test  for in  Bismuth  test 93 

Albumins,  derived 109  Black  precipitate la 

Albuminates 109  Boettcher's  test 93 

Alcohol,  amylic 26  Bromine,  qualitative  test  for 37 

butylic 26  quantitative  determination  of   ....    46 

definition  of 26  Bruecke's  lead  process 96 

ethylic 26  Butane 26 

methylic 26  Butene 25 

propenyl 27  Butyl 26 

propylic 20  _  .     ,  ,     .     , 

radicals,  definition  of  .  .26  Calculi,  phosphatic,  forms  of 83 

tables  oi    ....  .26  Cane  sugar  .   .  9x 

synthetical  production  of 8  _     composition  of 91 

Alcohols,  monohydric .26  Carbamic  acid 14 

primary    ...  .    »8  Carbamide 14 

secondary 28  Carbinol       ....        - 28 

table  of  36  Carbohydrates,  definition  of  .......      6 

tertiary.   '.  '.    29  Carbolic  acid a3 

triatomic .    27  antidote  for a3 

Aldehyde,  butylic a7  Carbon,  qualitative  test  for  35 

ethylic  27  quantitative  determination  of    ....    38 

propylic    !  1    a7  Cellulose  ......       13 

methylic  27  Chlorine,  qualitative  test  for 37 

valeric  '    27  quantitative  determination  of    ....    46 

Aldehydes,  definition  of '.    '.  '.    26  Composition  of  compounds  . 35 

table  of  27  Compound  radical,  definition  of 5 

Alkarsin  '    10  Correction  for  barometric  pressure  ....    69 

Alloxan  '    85  Correction  for  temperature 69 

Alloxantin   .'   .'   .'   .'   .'   .'   .    ."  .'   .    .'   .'   .'   .'   .'    85  Creatinine  87 

Alpha-naphthol  .    .  .    99  properties  of       ..........    88 

Amido-benzol  21  quantitative  determination  of    ....    88 

mercuric  chioride '.    12  l?sts  f°r    • f 

mercurous  chloride .12  „     zinc  chloride    ........    88 

Ammonium  carbamate 14  Cyanogen,  synthetical  production  of ...      7 

Amygdalin 33  Davy's  method  for  determining  urea  .       .    65 

Analysis,  elementary 37  Decomposing  agents,  acids    .  .    31 

method  of 38  alkalies      .  .    oa 

requisites  for 38  heat  | 

organic 35  oxygen '.    |o 

proximate 35  Derived  albumins     .  100 

qualitative    .    . 35  Dextrine   .  .    oi 

ultimate    -.-••••-. 35  Dextrose  ...  .90 

conditions  observed  in 37  Diacetic  acid  its 

Aniline  ...  21  test  for .'.'.'.'.  115 

Antipynn,  formula  of 14  Diastase  no 

Aqueous  vapor,  correction  for 70  Dimethylamide      '.  '13 

table  of  tension  of 71  Dimethylarsin     . '.    10 

Arabinose 91  Dumas'  method  for  determining  nitrogen     41 

Arsemcum 19 

antidote  for ai  Earthy  phosphates 78 

fatal  quantity  of 20  quantitative  determination  of    ....    8a 

Marsh's  test  for 23  Empirical  formula,  definition  of 15 

quantitative  determination  of    ....    29  method  of  determining 46 

17  (131) 


132 


INDEX. 


PAGE  PAGE 

Eremacausis 30        Isomeric  compounds 24 

Ethane 26               divisions  of 24 

Ethene 25               examples  of 24 

Ether,  amylic 37        Isomerism,  definition  of 24 

definition  of 27       Isuretine 62 

ethylic 27 

methylic 27  Johnson's  test     .  93 

propylic 27 

Ethers,  definition  of 27  „   ,     ,   . 

Ethers  table  of 27        Kakodyl  .   .           to 

Ethyl 26                compounds  of 10 

urethan                                                        14        Kakodyhc  acid      10 

properties  of 10 

Fat  acids,  definition  of 27  Kekulg's  benzol  ring    .... 

table  of                                                        27       Ketone,  definition  of 29 

Fehling's  solution,  clinical  use  of'   .'   .'   .'   .'105  Kjeldahl's  method  for  determining  nitre- 

preparation  of 102                   8en 45 

table  for  clinical  method to6 

Fehling's  test 97        Lactose 34 

method  of  applying 97        Laevulose 90 

Ferment,  definition  of 33        Lead  process 96 

Fermentation,  acetous 34  Liebig's  method  for  the  determination  of 

alcoholic 34                  sodium  chloride 61 

butyric 34               practical  application  of 62 

conditions  necessary  for  ...    •  .   .    .     53  Liebig's  method  for  the  determination  of 

definition  of 33               urea 71 

lactic 34               corrections  for 74 

test  for  glucose 93              practical  application  of 74 

varieties  of 33        Lithic  acid 84 

vinous 34 

viscous 35        Maltose 91 

Fermentescible  body ...    33        Mannitose 90 

Formic  acid 27  Marshall's  apparatus,  method  of  using  .   .  68 

synthetical  production  of 8        Marsh's  test 123 

Formulas,  deduction  of 46        Meta  compounds 22 

Fowler's  modification  of  Davy's  method  Metameric  compounds,  definition  of ...  24 

for  determining  urea 66        Methane 26 

Fruit  sugar 91        Methene 25 

Methyl 25 

Globulins 109        Methylamide 13 

test  for 112        Methyl-ethylamide 13 

Glucose     •••••••• 9°        Methyl-ethyl-propylamide 13 

alpha-naphthol  test  for 99        Methyl  urethan .14 

bismuth  test  for     93        Micrococcus  ureae 40 

Boettcher  s  test  for 93        Milk  sugar 

determination  of,  by  saccharimeter  .   .  107  Mohr's    method  for  determining   sodium 

fermentation  test  for 93  chloride     ...  56 

Fehling's  test  for 97                practical  application  of 59 

Johnson  s  test  for 93       Molecular  formula,  definition  of 15 

Moore  s  test  for             ••••••••    9*               method  of  determining 15 

phenylhydrazmehydrochloride  test  for  98  of  non-vaporizable  substances  .   ...  17 

picric  acid  test  for 93  Molecular  weight,  method  of  determining  15 

qualitative  tests  for   .   ......    92        Molisch's  tests 99 

quantitative  determination  of,  by  clin-              Moore's  test 92 

ical  method 105  Morphine,  tests  for  .'                                      .'  130 

Fehlmg's  solution 102  Mucin  91 

fermentation    .........    93        Murexide  test 85 

Robert  g  differential  density  me-  Mycodermae  aceti 

thod TOI 

thymol  test  for       100  Naphthalene   .                                               .  99 

Trommer  s  test  for 94       Native  albumins 108 

•Glycendes 08  Nitrogen,  Dumas'  method  for  determining  41 

Glycerine 27  gravimetric  determination  of     ....  43 

Grape  sugar    ••••-..••- 9°  Kjeldahl's  method  for  determining  .    .  45 

Graphic  formula,  definition  of 20              qualitative  tests  for 35 

Haycraft's  method 87  quantitative  determination  of    ....  41 

Heller's  method no  volumetric  determination  of  .....  44 

Hemialbumose  .                                           .  112  W™    and.   Varrentrapp  s  method  for 

Hippuric  acid 86       „.       determining            4z 

Homogentisic  Acid,  test  for 98       Nitrogenous  compounds 6 

Homologous  series,  definition  of .   .    .  • .   .    25  „.  ,          ,  ,.   .  .     '    ,. 

table  of  an                                                  25       defines,  definition  of 25 

Hydrocarbons,  definition  of _   .  table  of 25 

Hydrogen,  qualitative  detection  of .   ...    35        Opium,  tests  for. 129 

quantitative  determination  of    .            .38        Organic  body,  definition  of. 7 

Hypobromite  method  for  determining  urea    67                chemistry,  definitions  of 5 

compounds,  saturated n 

Inosite 90               matter,  tests  for 35 

Iodine,  qualitative  test  for 37  substances,  decomposition  of    ....  30 

quantitative  determination  of    .   .       .46        Ortho  compounds 22 


INDEX. 


133 


PAGE 

Para  compounds 23 

Paraffins,  definition  of 26 

table  of 26 

Pentane 26 

Pentene 25 

Penicilium  glaucum 34 

Phenol 23 

Phenol-sulphuric  acid 23 

Phenylhydrazine  hydrochloride 98 

Phosphoric  acid 78 

indicator  in 80 

practical  method  for  determining     .    .  Si 
principles  of  volumetric  determination 

of 78 

volumetric  determination  of 81 

Phosphorus,  qualitative  tests  for 36 

quantitative  determination  of    ....  46 

Picric  acid  test  for  glucose     .......  93 

15 

'7 
16 


Poison,  definition  o 

Poisoning,  appearances  common  to 

sources  of  evidence  in 

symptoms  of  arsenical     .... 
Poisons,  causes  which  modify  .    .    . 

classification  of 

limit  of  tests  for 

toxic  action  of 

Polymeric  compounds,  definition  of       .    .  24 

Potass-amide 13 

Potassium  ferrocyanide  test  for  albumin  .  in 

Pressure,  correction  for  barometric     ...  69 

Propane 26 

Propene 25 

Propyl 26 

Propylic  acid 27 

Proximate  principles,  definition  of  .    ...  7 

analysis,  definition  of 35 

Putrefaction,  definition  of 32 

Radical,  definition  of 8 

electrical  condition  of 8 

Radicals,  equivalence  of 8 

types  of 9 

Rational  formula,  definition  of 20 

Raoult's  method  for  determining  molecular 

formula 18 

Reinsch's  test 123 

Results,  calculation  of 46 

Roberts'  differential   density  method   for 

determining  glucose 101 

Saccharimeter 107 

Saccharose 91 

Salkowski-Ludwig  method 87 

Schiff 's  test  for  uric  acid 85 

Soda-lime,  composition  of 32 

Sodium    chloride,    Liebig's    method    for 

determining 61 

gravimetric  determination  of     ....  54 

Mohr's  method  for  determining  ...  56 

Sodium  hypobromite  solution 68 

Sorbine 90 

Standard  solution  of  mercuric  nitrate  for 

determining  sodium  chloride     .   .    .  61 
of  mercuric  nitrate  for  determining  urea   72 

of  phosphoric  acid 79 

of  silver  nitrate 57 

corrections  for 58 

of  uranium  acetate 79 

of  uranium  nitrate 79 

Starch 91 

Stearin 28 

Strychnine,  tests  for 130 

Substitution,  definition  of II 

examples  of 12 

Sugars 90 


FAGK 

Sulphur,  qualitative  analysis  of 36 

quantitative  determination  of  ....  45 

Synopsis  of  albumins 108 

Synthetical  production  of  alcohol  ....  8 

benzaldehyde 8 

cyanogen 7 

formic  acid 8 

Synthetical  production  of  urea 7 

Temperature,  correction  for 69 

Thymol  test 100 

Toxicology 115 

Trimethylamide 13 

Trinitrocellulose 13 

Trinitroglycerine 13 

Trommer's  test 94 

Type,  definition  of n 


Uranium  acetate  solution,  standardization 

of 81 

Urea 6a 

artificial  preparation  of 63 

Davy's  method  for  determining  ...  65 
Fowler's  modification  of  Davy's  meth- 
od for  determining 66 

hypobromite  method  for  determining  .  67 

Liebig's  method  for  determining     .   .  71 

methods  of  obtaining  from  urine  ...  63 

nitrate  of 64 

oxalate  of .'   .  64 

preparation  of  standard  solution  of .   .  73 

properties  of 64 

qualitative  tests  for 65 

quantitative  determination  of    ....  65 

special  history  of 62 

synthetical  production  of    ......  7 

Urethan 14 

Urethans 14 

Uric  acid 84 

properties  of 84 

qualitative  tests  for 85 

quantitative  determination  of    ....  86 

salts  of 85 

Urine 48 

abnormal  constituents  of 91 

accurate  method  for  determining  quan- 
tity of  solid  matter  in 51 

acidity  of 50 

amphoteric  reaction  of 49 

analysis  of 33 

approximate  method  for  determining 

quantity  of  solid  matter  in 52 

average  quantity  voided 53 

collection  of 49 

determination    of    quantity   of  solid 

matter s1 

diabetic 92 

method  of  determining  acidity  of    .   .  50 

methods  of  obtaining  urea  from    ...  63 

properties  of  diabetic   .   .    • 92 

reaction  of  .   .    .    .  • 49 

specific  gravity  of 59 

table  of  average  composition  of   ...  53 

Valeric  acid 27 

Victor  Meyer's  method 15 

Vital  force 5 

Weyl's  test  for  creatinine 88 

White  precipitate 12 

Will  and  Varrentrapp's  method  for  deter- 
mining nitrogen 42 


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